National Astronomy Meeting (NAM) 2025

7 Jul 2025, 08:00 → 11 Jul 2025, 18:55 Europe/London

Teaching and Learning Centre (TLC)

David Alexander (LOC; chair), Mathilde Jauzac (SOC; co chair), Peter Wyper (SOC; co chair) (Durham University)

Image credit: Durham University

The Royal Astronomical Society is proud to present the next National Astronomy Meeting, NAM2025, at Durham University from Monday 7th July to Friday 11th July, 2025. It is organised in conjunction with Durham University's Centre for Extragalactic Astronomy, the Centre for Advanced Instrumentation, the Institute for Computational Cosmology, the Institute for Particle Physics Phenomenology, and the Department of Mathematical Sciences.

NAM2025 covers the full range of astronomy research in the UK, including the instrumentation and astro-particle communities, as well as other key issues relevant to the UK astronomy community. Beside the UK’s astronomy community, the meeting includes the UK Solar Physics (UKSP), and the Magnetosphere Ionosphere and Solar-Terrestrial (MIST) communities.

It is centrally located in the modern purpose-built Teaching and Learning Centre (TLC) and the opposing Ogden Centre West (OCW) building which hosts the majority of the astronomy research at Durham University.


Image credit: Durham University

NAM2025 is a hybrid conference but where the majority of participants are expected to attend in person. By using a hybrid model we aim to allow as many people as possible to experience the conference and learn about the exciting astronomy and space science research being conducted around the UK and further afield.

The theme for NAM2025 will be "community" to reflect our broad engagement programme, with extensive schools, outreach, art, heritage, and industry elements, in addition to the regular scientific and professional practice sessions. The theme of community also broadly reflects the need for us to work together to achieve greater things, particularly during these challenging times both within the UK and across the globe.

The organisers of NAM2025 have made sustainability a high priority, and will aim to minimise waste produced during the meeting and highly encourage delegates to use public transport when travelling to Durham in the UK and to car share when driving is required.

Latest news:

26/06/25: Release of Zoom access details (links, meeting codes, passcodes) will take place on Sunday 6th July. They will be visible to all registered participants on your webpage. Please ensure you're logged in on our webpage, and the email address of your account matches the email address provided during registration/payment processs (more on that on our FAQ page).

17/06/25: Due to the large demand to present scientific posters at NAM2025, all posters must be printed in A1 (841mm x 594mm; 33.1" x 23.4") and in a landscape orientation. Any posters which do not conform to these size and orientation constraints cannot be displayed.

17/06/25: A Presenter (talks and posters) Guide and Session Organiser Guide have been produced to aid in the smooth running of the parallel and lunchtime sessions. We encourage all presenters and session organisers to read the guides prior to the start of NAM2025.

05/06/25: The Royal Astronomical Society have announced a Carer's Grant to support those with caring duties over the week of NAM. The application form can be found on our Accessibilty page and must be returned to awards@ras.ac.uk. The deadline is 17:00 BST on 4th July 2025.

05/06/25: NAM will host a 3-minute thesis competition on Thursday 10th July at 6pm with a total prize of £100 (1st £60, 2nd £25, 3rd £15, in Amazon vouchers). If you are a student or early-career researcher attending NAM, this is a fantastic opportunity to hone your communication skills, gain visibility, and engage with the broader community. Sign up now by filling in this form before 14:00 BST on 15th June 2025: 15 candidates will be selected to present. The selected candidates will be provided with help and support to prepare for this inspiring event.

23/05/25: We are pleased to announce the release of the full conference timetable. We are finalising some of the timetable details and will keep updating it in the run up to NAM2025. Note for presenters where your name is not visible for your talk in the schedule - this is quickly and easily fixable in your "Contribution", see our FAQs for information.

15/04/25: For those participants presenting at NAM (giving either a talk or a poster), the registration deadline is 6th June, 2 weeks earlier than the regular participant deadline. We need to set this earlier presenter deadline as there are many programme-related details that need to be sorted out well in advance of the start of NAM.

15/04/25: We are pleased to be able to support a small number of fee waivers for those in greatest need who do not have alternative funding options. The deadline for applications is 14th May 13:00 BST.

15/04/25: The deadline for booking a room at the Radisson Blu using our NAM block booking is 1st May.

06/04/25: The block schedule showing the days and times for all of the parallel and lunchtime sessions has been published.

02/04/25: Following the deadline for the NAM2025 Call for Abstracts, we have generated two plots illustrating the submission trends. These plots show the number of abstracts submitted over time, the green line shows the cumulative numer while the red line illustrates the daily rate:

We received ~900 abstracts in total, with ~800 requests for talks and ~100 requests for posters: thank you all for your fantastic response to NAM2025! The individual session organisers will now assess the abstracts submitted to their sessions and decide on the selected talks and posters, following the session organiser guidelines, with a deadline of 25th April.

04/02/25: The selected parallel and lunchtime sessions have been published.

See below for key dates including the participant registration deadline to attend NAM2025.

Key dates:

Parallel session proposal submission: 14th October-6th December
Announcement of participant registration: 4th February
Announcement of parallel sessions: 4th February
Abstract submission: 4th February-31st March
Announcement of block schedule: 6th April
Announcement of full conference timetable: 23rd May
Registration deadline: 6th June (poster and talk participants), noon (12:00 BST) 20th June (regular participants)
Release of Zoom access details: 6th July

Welcome reception: 6pm on 6th July
Start of conference: 8am on 7th July
End of conference: 4pm on 11th July

                        

 

posters NAM2025-PosterMaps.pdf posters.pdf

Session_timetable_template Timetable_template.csv

Monday 7 July

08:00 Registration and set up

The ultimate fate of multi-phase gas in galaxies: from giant molecular clouds to the virial radius

Organisers: Bronwyn Reichardt Chu, Thomas Rintoul; co organisers: Alex Cameron, Fred Jennings, Seoyoung Lyla Jung, Hengxing Pan, Martin Rey, Tianyi Yang

The baryon cycle regulates star formation and shapes galaxies across cosmic time. Gas is accreted onto galaxies from the circumgalactic medium (CGM), used as fuel for star formation, stirred up by young massive stars, and expelled out of galaxies by stellar feedback processes, contributing back to the CGM where it can cool and reaccrete. Characterising multiphase gas - its structure and dynamics, the impact of stellar feedback, and its interplay with local, galaxy and cluster scale environments - is a key problem of modern galaxy formation.

There are many challenges in both observing and simulating the full baryon cycle. Gas is impacted over a vast range of scales, from individual massive star winds, ionising radiation and explosions (~pc) to star formation-driven galaxy-scale outflows contributing to the CGM (~100s kpc) and IGM (~Mpc). In addition, gas within and surrounding galaxies is intrinsically multiphase, spanning more than 8 orders of magnitude in both density and temperature. This requires the combination of multi-wavelength observational data and high-resolution simulations on a range of scales to form an understanding of the role of gas within galaxies.

This session seeks to bridge the gap between observers and simulators to discuss recent progress towards tackling these challenges, solidifying our current understanding of questions such as “How can we constrain the physics driving the baryon cycle?”; “What effect does environment have on the multiphase baryon cycle?”; “How can we connect the effects of feedback across scales?”; and “How can we best use numerical simulations to interpret and inform observations of multi-phase gas in and around galaxies (and vice versa)?”

09:00 Prep time

1 The impact of feedback on the distribution of baryons within and beyond haloes

Stellar and AGN feedback shape star formation and baryon distribution across cosmic time, yet their detailed mechanisms remain uncertain. A major challenge is their multi-scale impact, extending from galaxies to the circumgalactic and intergalactic media (CGM and IGM).

Observations of gas in absorption and emission, combined with hydrodynamical cosmological simulations, provide critical insights into the baryon cycle. I will review key findings from more than two decades of CGM and IGM studies, highlighting how feedback processes influence the evolution of gaseous phases from galaxies to the virial radius and beyond.

Focusing on predictions from the Simba simulations, I will examine baryonic phase distributions across halo masses ($10^{11}–10^{14}$ $\mathrm{M}_{\odot}$) and redshifts ($0 < z < 4$). Simba reveals that AGN-jet feedback produces gentler gas radial declines in gas density profiles around galaxy groups and clusters, while stellar feedback dominates below $\sim 10^{12.5}$ $\mathrm{M}_{\odot}$.

To complement these results, I will present preliminary results from the FLAMINGO simulations, which incorporate eight feedback models and explore a wider mass range with larger box sizes ($1.0–2.8$ $\rm Gpc$). These results underscore the sensitivity of gas density evolution to sub-grid physics and highlight pathways for refining feedback models.

By integrating insights from Simba, FLAMINGO, and multi-wavelength observations of various gas phases within and beyond galaxies (e.g., MUSE, eROSITA), we can tightly constrain feedback models and clarify their role in baryon cycling across both large and small scales.

Speaker: Daniele Sorini (Durham University)

2 Emission line diagnostics in H II regions: a non-equilibrium perspective

Recent advancements in instrumentation have enabled the investigation of star-forming regions in nearby galaxies with unprecedented spatial resolution. To facilitate detailed comparisons between simulations and observations, we generate mock emission line maps based on a state-of-the-art simulation of an ideal H II region, utilizing a novel post-processing pipeline. This simulation couples radiation hydrodynamics (SWIFT-RT) with a non-equilibrium photochemistry network (CHIMES), incorporating 157 chemical species.
In this talk, I will introduce a new atomic model that accurately predicts hydrogen recombination line emissivity. This model is computationally efficient and can be seamlessly integrated into post-processing workflows for hydrodynamic simulations. By applying it to our new simulation, we gain new insights into emission line diagnostics in a non-equilibrium setting, which was previously unattainable. I will then explore widely used diagnostic tools in the ISM community, highlighting their deviations from traditional equilibrium-based predictions.
Our new atomic model and post-processing pipeline significantly enhance our ability to study emission line diagnostics from a non-equilibrium perspective. The atomic model, together with the pipeline, steps towards bridging the gap between simulations and observations, providing insights into the physical conditions of star-forming regions and contributing to the refinement of theoretical models.

Speaker: Yuankang Liu (Durham University)

3 Feedback in dusty elliptical galaxies

The way galaxies stop forming new stars is a key aspect of galaxy evolution. This is connected with feedback process causing the removal of gas, the fuel of star formation. I will present a novel way to study the interstellar medium (ISM) removal by selecting dusty early-type galaxies detected by Herschel, for which the decrease of gas and dust can be tracked as a function of age. The observations of their dust, molecular and atomic gas content, and optical spectral classification led to the first direct measurement of the ISM removal timescale and to the conclusion that the cold ISM is likely removed by feedback from old stellar populations (either by planetary nebulae or cosmic rays). This feedback is often not considered in the context of quenching of star formation. Low star formation efficiencies (SFE) and normal gas fractions indicate that quenching is not due to running out of gas, but due to gas becoming unable to form stars.

Speaker: Michał Michałowski (Adam Mickiewicz University in Poznan)

4 The role of star formation-driven outflows in the baryon cycle

Outflowing gas driven by star formation plays a critical role within the baryon cycle. However the details of this stellar feedback process are still unclear, particularly in starbursting environments. To better constrain the feedback models used to understand galaxy evolution, high resolution IFU observations are needed to spatially resolve star formation-driven outflow properties and link these to co-located galaxy properties. I will present results from the DUVET survey of starbursting galaxies observed using the IFU KCWI. We measure outflows in 10 face-on local galaxies with ~1000 lines of sight of individual outflow measurements at 500pc resolution. Using our observations, (1) we are able to discriminate between widely used models of the launching mechanism of the outflow. (2) We derive much needed scaling relations for the relationship between star formation and outflow properties. (3) We compare to observations from NOEMA, and connect the outflows with location in the resolved Kennicutt-Schmidt relation to find that starburst regions remove more gas via the outflow than they convert into stars. This directly measures how outflows regulate star formation and contribute to the baryon cycle. (4) Finally, we develop a non-parametric method to measure outflows in emission lines. We map the mass of outflowing gas reaching velocities high enough to leave the galaxy and compare this to gas which likely remains within galaxy fountains. DUVET's sample of resolved outflows provides a new perspective to make ground-breaking constraints on how stellar feedback regulates star formation, contributes to the baryon cycle, and drives galaxy evolution.

Speaker: Bronwyn Reichardt Chu (Durham University)

5 Relaxation timescales of stellar-gas misalignments in the EAGLE simulation

Mergers and accretion events are a key element of the baryon cycle, and have strong impacts on the distribution, kinematics and mixing of gas in galaxies. Major mergers are well studied in this regard, but gas-rich minor mergers and cold gas accretion are much less well constrained. A key probe of these external gas accretion events are kinematic misalignments between the stellar and the cold gas components. In the absence of continued smooth accretion, misalignments are predicted to be short-lived (lifetimes ~100 Myr). However, such short relaxation timescales are unable to explain the distribution of misalignments observed in ~40% of early-type galaxies (ETGs).

In this talk, I am going to present the results obtained by using the EAGLE cosmological simulation to investigate the stellar-gas misalignment relaxation timescales over a large, representative galaxy population (approx. 5,600 galaxies) from present day to z=1. We show for the first time that misalignments have relatively short median relaxation timescales of ~500 Myr, with ~20% of misalignments persisting on timescales significantly longer than predicted. Additionally, misalignment formation coincides with mergers in only ~17% of cases. Our results point toward cold gas replenishment in massive galaxies occuring through diverse pathways, with halo cooling and accretion playing an important role in maintaining misalignments in massive galaxies. The use of EAGLE and future cosmological simulations allows us to constrain the internal and external processes through which galaxies can replenish their cold gas that fuel star formation and AGN activity in massive galaxies.

Speaker: Maximilian Baker (Cardiff University)

6 Observations of cooling flows in nearby elliptical galaxies and the fate of cooled gas

The radiative cooling time of hot gas at the centres of many cool cores in clusters of galaxies & massive elliptical galaxies is short, dropping below $10^8$ years. At the same time, the mass cooling rates inferred from simple modelling of X-ray observations of these objects are very low, indicating that either AGN feedback is tightly balanced or that the soft X-rays from cooling gas are somehow hidden from view. This Cooling Flow Problem has been extensively studied in galaxy clusters, but in our work we tackle this problem in elliptical galaxies. An intrinsic absorption model, originally developed for application to galaxy clusters (Allen & Fabian 1997), is applied to search for hidden cooling flows (HCFs) of gas in seven nearby elliptical galaxies (z~0.001-0.007). We find that intrinsic photoelectric absorption can explain the observed lack of strong soft X-ray emission from cooling flows in the spectra of elliptical galaxies. Hidden mass cooling rates of ~0.5-8 $\text{M}_{\odot} \ \text{yr}^{-1}$ are identified in each galaxy, with absorbed emission ultimately emerging in the far-infrared (FIR) band. In each galaxy, the cooling flow luminosity calculated from the inferred HCF rate was found to agree with the observed FIR luminosity. The discrepancy between calculated HCF rates and observed normal star formation rates suggests an alternative fate for the cooled gas, with low-mass star formation considered as the primary outcome.

Speaker: Lucy Ivey (Kavli Institute for Cosmology, University of Cambridge)

10:23 Poster Flash Talks

Ryan Roberts, Ting-Yun Cheng, Lilia Magnus

The Dusty Universe - Near and Far

Organisers: Andrew Blain, David Clements, Stephen Eales, Matt Griffin, Pamela Klassen, Seb Oliver, Kate Pattle, Chris Pearson, Dimitra Rigopoulou, Carole Tucker

Dust is a significant constituent of the ISM, is strongly involved in many important processes on all scales, including star formation, planet formation, ISM enrichment, and AGN structure, and hides the physics and chemistry of these processes behind a veil of obscuration. Observations at mid-IR, far-IR and submm wavelengths provide direct observations of thermal emission from this dust and allow spectroscopy to penetrate the obscuration. With the legacy of Herschel, continuing operations at JCMT and ALMA, with JWST allowing high resolution mid-IR observations, we are at a key point in our ability to understand the dust and gas in obscured regions in nearby systems, and out to the most distant objects known. Forthcoming projects, including the Simons Observatory, PRIMA and AtLAST, will provide critical new insights. This session will explore our current understanding of the dust-obscured universe, examining synergies between local and distant universe studies, and assessing what next steps are needed - observationally, theoretically and in instrumentation - to better understand the role and importance of dust and obscured processes in the universe.

7 PEBBLeS in Protoplanetary Discs

I report on the Planet Earth Building Blocks Legacy e-MERLIN Survey. PEBBLeS is an SKA Cradle of Life forerunner project, and has just completed a census of very large dust grains in massive discs in northern star-forming regions. We uncover where dust is growing large enough to overcome loss processes and so can proceed to make planets. The e-MERLIN resolution is very high and can find the seeds of planets inwards of Jupiter's orbit. We find that observations at shorter wavelengths, including ALMA, have little predictive capability to tell us where planets will form. Questions this leads to in the SKA era will be discussed.

Speaker: Jane Greaves (Cardiff University)

8 Understanding the evolution of dust near and far using the Colibre suite of simulations

Recent years have seen significant improvements in computational codes and hardware, incorporating novel physics and strategies to statistically explore and understand galaxy formation and evolution. A recent addition to this landscape is the COLIBRE (COLd ISM gas and Better REsolution) suite of simulations, built on the open source SWIFT simulation code. The suite of simulations includes the full multi-phase ISM with non-equilibrium (H+He) chemistry and an active dust model. It includes new prescriptions for star formation, stellar feedback, and SMBH seeding, growth, dynamics, and feedback.

The dust model in COLIBRE tracks the evolution of carbonaceous and silicate grains in large and small grains, through stellar seeding, grain growth in dense gas clouds, sputtering, shattering, coagulation, etc. It acts as catalysts for gas cooling, as they are self-consistently coupled to the chemical network within the simulation.

In this talk, I will present the predictions from the model, focusing on key observational dust relations such as the evolution of the galaxy dust mass, dust-to-gas ratio, dust-to-metal ratio and the dust mass function. The predictions align well with the observations in the low-redshift (z<=2) regime, though tensions arise in the high-redshift Universe. These tensions can be mitigated by considering the presence of hot dust in the early Universe. I will also explore the distribution of dust in the various gas phases as well as in the circumgalactic medium. I will further investigate the evolution of grain size distribution in the galaxies, self-consistently building the dust attenuation curve, providing a framework for its evolution.

Speaker: Aswin Payyoor Vijayan (University of Sussex)

9 Magnetic fields in the interstellar medium: current achievements and future perspectives

Advances in submillimetre dust emission polarimetry are revolutionizing our understanding of the magnetic fields which thread the interstellar media of the Milky Way and other galaxies. In this talk I will discuss the insights which we are gaining into the energy balance, dynamics and evolution of the magnetized interstellar medium from recent observations made with the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). These observations span size scales ranging from nearby star-forming regions, observed as part of the JCMT BISTRO Survey, to the magnetic fields of starburst and interacting galaxies. I will discuss how we can infer the dynamic importance of magnetic fields from observations of magnetic field geometries in the dense interstellar medium, and the emerging evidence for how the interaction between magnetic fields, outflows and feedback may influence star formation efficiency on both small and large scales. Finally, I will discuss the prospects of future far-infrared and submillimetre polarimetry with PRIMA and AtLAST.

Speaker: Kate Pattle (University College London)

10 Simulating dust production, growth and destruction in the ISM on a cosmological scale

The evolution of dust is important for understanding galaxy evolution. More detailed models of dust formation are needed to reproduce observations of dust in galaxies at high redshift, which include high dust-to-stellar mass ratios in z~7 galaxies observed with ALMA. At the same time, the moderate amount of dust at z~14 seen with JWST requires processes such as dust destruction by the supernova reverse shock to reproduce in models. A better understanding of dust reddening and extinction is also necessary to more accurately analyse observations of galaxies. Therefore, we introduce a dust model into our cosmological hydrodynamical simulations. Our code is based on GADGET-3 but includes the latest nucleosynthesis yields to trace the evolution of elemental abundances in detail as well as all necessary baryon physics such as radiative cooling, AGN, star formation and supernova feedback. We trace the mass of carbon, iron, alumina and different species of silicate dust grains in the interstellar medium (ISM). Dust grains are produced by core-collapse supernovae and Asymptotic Giant Branch stars and are distributed into the ISM. The dust mass is further increased by accretion from the gas phase or decreased by star formation, supernova shock waves and thermal sputtering. We then compare our results with observations from both high redshift and the local universe.

Speaker: Alice Ferreira (University of Hertfordshire)

11 Disentangling the [CII] deficit: an ALMA survey of [CII] and [NII]205 in z~4.5 SMGs

The bright [CII] 158 micron line can emit up to 1% of a galaxy's far-IR luminosity and has been suggested as an efficient tracer of star-formation in high-redshift galaxies, where it is shifted in to ALMA bands 4–7. However, a deficit of [CII] relative to IR luminosity is observed in galaxies with L_IR>10^11 L_sun, and the origins of this deficit are not yet fully understood, limiting its reliability as a star-formation tracer. Furthermore, [CII] can be be emitted from regions dominated by both neutral and ionised hydrogen, which further complicates interpretation of [CII] emission. I will present the results of a ALMA survey of both [CII] and [NII] 205 micron in 12 ALESS and AS2UDS submillmeter-selected galaxies at z~4.5. [NII] has a higher ionisation energy but similar critical density to [CII], so it can only be emitted from ionised regions of the interstellar medium. The ratio of [CII] to [NII] in our sample shows that ~75–95% of the [CII] originates from photodissociation regions and that this fraction is correlated with the strength of the [CII] deficit in each galaxy. I will also show the results of a dynamical analysis of our data.

Speaker: Julie Wardlow (Lancaster University)

12 Dust-obscured star-formation history back to z ≃ 7 revealed by ALMA and JWST PRIMER

We use the deep imaging from the JWST PRIMER survey to study the properties of (sub)mm sources detected by ALMA in the centre of the COSMOS field, with the aim of better constraining the history of dust-enshrouded star formation. The wealth of ALMA data in this field enabled us to isolate a robust sample of 128 (sub)mm sources, spanning two decades in (sub)mm flux density. The JWST imaging is deep/red enough to reveal secure galaxy counterparts for all of these sources. Moreover, 52% of the galaxies have spectroscopic redshifts, enabling us to refine the photo-zs for the remaining galaxies. Armed with this robust redshift information, we calculate the star-formation rates (SFR) and stellar masses of all 128 ALMA-detected galaxies, and place them in the context of other galaxies in the field. We find that the vast majority of star formation is dust-enshrouded in the ALMA-detected galaxies, with SFR ranging from $\sim1000$ down to $\sim20\,\rm{M_{\odot}\,yr^{-1}}$. We also find that virtually all ($126/128$) have high stellar masses, at all redshifts, with $M_*>10^{10}\,\rm{M_{\odot}}$. The unusually high quality of our sample enables us to make a robust estimate of the contribution of the ALMA-detected galaxies to cosmic star-formation rate density (SFRD) from $z=2$ out to $z=7$. Finally, we use our knowledge of all other massive galaxies in the field to produce a completeness-corrected estimate of dust-enshrouded cosmic SFRD. This confirms that UV-visible star formation dominates at $z>4$, but also indicates that dust-enshrouded star formation likely still made a significant contribution at higher redshifts.

13 Dust in the Universe, and what AtLAST can tell us about it.

Current single-dish sub-mm facilities have opened new views of some of the brightest celestial sources, and interferometers have provided the exquisite resolution necessary to analyse the details in small fields. Answering questions with current generation facilities is creating the next generation questions. To go further, what we need is a facility capable of rapidly mapping large portions of the sky both spatially and spectrally, but also repeatedly. The Atacama Large Aperture Sub-millimeter Telescope (AtLAST) aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned sub-mm telescopes. With its 50m dish and large field of view, the strength of AtLAST is in science where a large field of view, highly multiplexed instrumentation and sensitivity to faint large-scale structure is important: from the gas and dust that fills and surrounds galaxies to our own Solar System. In this talk, I will present an overview of some of the dust focused science that AtLAST will be able to deliver.

Speaker: Pamela Klaassen (UK Astronomy Technology Centre)

14 The Probe far-infrared Mission for Astrophysics PRIMA

Recently the PRIMA mission was selected by NASA for Phase A study. If it is selected for implementation in April 2026 it will be the first far infrared astrophysics observatory for 22 years when launched in 2031.

The observatory provides unique spectral, imaging and polarimetry capabilities from 24-235 micron with sensitivity orders of magnitude better than predecessors. PRIMA is designed to deliver key science on: the origin of planets and their atmospheres; the co-evolution of galaxies and supermassive black holes since cosmic noon; and the buildup of dust and metals.

In this talk I will outline the technical capabilities of PRIMA, briefly describe the science programme and the opportunities and plans for UK involvement.

Speaker: Seb Oliver (University of Sussex)

10:16 Poster Flash Presentations

Next generation solar physics – preparing for MUSE and Solar-C

Organisers: Sarah Matthews, Patrick Antolin, Ineke De Moortel

In 2017 the international solar physics community agreed the highest priority science questions for solar physics in the coming decade and the measurements and instruments needed to answer those questions:
o Formation mechanisms of the hot and dynamic outer solar atmosphere
o Mechanisms of large-scale solar eruptions and foundations for predictions
o Mechanisms driving the solar cycle and irradiance variation

The realisation of those recommendations is the combination of two complementary solar space missions: NASA’s MUlti-slit Solar Explorer (MUSE) and JAXA’s multi-agency Solar-C. MUSE (launch 2027) will be a unique multi-slit spectrograph able to provide imaging spectroscopy of the corona at multiple wavelengths up to 100 times faster than current instruments. Solar-C (launched 2028), combines the EUV High-throughput Spectroscopic Telescope (EUVST) and the Solar Spectroscopic Irradiance Monitor (SoSpIM). EUVST will seamlessly and simultaneously observe a range of temperatures spanning more than three orders of magnitude from the chromosphere to the corona, providing unprecedented plasma diagnostic capability, while SoSpIM will provide complementary EUV spectral irradiance measurements. The combination of MUSE and EUVST will revolutionise our ability to probe the multi-scale nature of the physical processes in the corona, from small-scale energy release to large-scale impacts.

Supported by STFC and ESA the UK is both developing the short-wavelength camera for EUVST and helping to develop the science and tools to exploit MUSE, EUVST and SoSpIM. This session will bring together observers, modellers and theoreticians to discuss current work and future directions on all relevant science topics to promote optimum UK science return.

15 The MUSE Mission

NASA's Multi-slit Solar Explorer (MUSE) mission is a new kind of spectrometer, targeted at spectroscopy of the rapidly evolving phenomena driving heating and dynamics of the solar atmosphere. MUSE is led by the Lockheed Martin Solar and Astrophysics Lab, with international science team involvement, including from the UK. Unlike previous space-based solar spectrometer designs in which a single slit rasters across a region of the solar surface at relatively low cadence, or executes sit-and-stare observations at significantly higher cadence, MUSE has an assembly of 35 slits each rastering across a narrow region of the Sun. This enables the coronal plasma to be measured across a field of view of 156" x 170", at 0.5" spatial scales, up to 100 times faster than previous instruments. MUSE's science goals are to determine which mechanism(s) heat the corona and drive the solar wind, to understand the origin en evolution of the unstable solar atmosphere, and to investigate fundamental plasma physics processes, and strong EUV spectral lines at 171, 284 and 108Å, plus context images at 193 and 304 A, span a range of temperatures have been selected to facilitate this. This talk will give an overview of the MUSE mission, and the kinds of science that it enables.

Speaker: Lyndsay Fletcher (University of Glasgow)

16 Probing pre-flare dynamics with the short-wavelength camera onboard the EUV High-throughput Spectroscopic Telescope on SOLAR-C

The EUVST spectrograph (EUV High-throughput Spectroscopic Telescope) onboard the upcoming SOLAR-C spacecraft (JAXA), scheduled for launch in the late 2020s, will simultaneously observe a wide temperature range: from the 10,000-Kelvin chromosphere to the million-Kelvin corona, and even to 10 million-Kelvin solar flares, allowing the continuous tracking of plasma and energy transport. The spectrograph consists of three long wavelength (LW) CMOS cameras (NASA/NRL) and one short wavelength (SW) CCD camera (ESA/UCL-MSSL) and will act as a successor to Hinode/EIS.

In this work, we use simulations from multidimensional MHD code MURaM and an accurate camera response model to analyse the expected performance of the SW camera. We use our framework to perform a Monte Carlo study and calculate the expected spatial and spectral resolution of the SW detector, along with the expected accuracy in Doppler velocity and excess broadening (non-thermal velocity) for the pre-flare atmosphere modelled by Cheung et al. (2019). We compare these results to recent studies of pre-flare non-thermal velocity with Hinode/EIS.

Speaker: James McKevitt (UCL)

17 New diagnostics for the chromosphere using emission lines from neutral carbon observed by EUVST

An important goal of the Solar-C EUVST spectrometer is to make seamless observations from the chromosphere to the corona. Within its spectral range are potentially hundreds of chromospheric lines from highly excited, Rydberg levels in neutrals. Since the majority of the lines form in LTE the modelling is greatly simplified, and yet their diagnostic potential has largely been untapped in the literature. Using recent atomic data for these lines in carbon, we have carried out radiative transfer calculations with the Lightweaver code to determine the conditions under which the lines form and their response to changes in atmospheric parameters. We found that the lines form low in the chromosphere, thus widening the expected range that EUVST will cover. The work also identified a number of neutral carbon lines that were either unknown or previously misidentified in quiet Sun spectra. The accuracy of the theoretical energies is such that these lines are useful references for wavelength calibration and Doppler measurements.

Speaker: Roger Dufresne

18 Observations of Chromospheric Condensation in the Si III 1206 Å line

During solar flares, nonthermal heating of the chromosphere induces overpressure, leading to explosive evaporation and consequent condensation to conserve momentum. While this phenomenon has been widely observed via Doppler shifts in various chromospheric and transition region lines, it has yet to be observed in the Si III 1206 Å line (logT≈4.7) which is set to be included in the SOLAR-C/EUVST LW3 band (1115-1275 Å). We analyse recently released spectral observations from SORCE/SOLSTICE, which rastered across the Si III 1206 Å and Lyman-alpha lines at a cadence of ~1 minute, to study the Doppler velocity in the Si III line for seven M- and C-class flares. By subtracting a pre-flare profile from disk-integrated flare spectra, we isolate the flaring component and fit Gaussians to measure Doppler shifts. Of the seven events, six exhibited redshifts in the line profile, indicative of condensation, with velocities reaching up to ~100 km/s. Intriguingly, two events show blueshifts, suggestive of upflowing material, with one transitioning from blueshift to redshift at the flare peak. These observed upflows may be chromospheric bubbles, where cooler chromospheric material is lifted by underlying evaporating material. Our findings establish the Si III line as a novel diagnostic for chromospheric mass motions, offering crucial insights into flare driven dynamics. These results should inform the interpretation of upcoming high-resolution SOLAR-C/EUVST imaging spectroscopy observations of Si III during Solar Cycle 25.

Speakers: Luke Majury, Ryan Milligan (Queen's University Belfast)

19 Flare lines in MUSE/EUVST

Hinode EIS observations of flares are used to discuss the potential diagnostics
of hot (5-15 MK) plasma for the short wavelength channel of EUVST.
Several lines, rarely or never observed previously, are reported.
Comparisons between theoretical and observed intensities is generally very good, using my recent EIS radiometric calibration. However, discrepancies are present for a few cases, indicating the need for new atomic calculations.

A new programme for laboratory astrophysics is presented. Electron Beam Ion Trap spectra will finally observe several EUV flare lines predicted to be visible but never observed. Also, detail analysis will help resolving the identifications of the forest of coronal lines that are blending the flare lines in the soft X-rays such as the Fe XIX line, the main target of MUSE.

Speaker: Giulio Del Zanna (University of Cambridge)

20 How different thermal transport mechanisms influence thermodynamic cycle of solar flares

Solar flares are the most powerful energy-release processes in the solar system. During the flare, a huge amount of energy is released in a relatively compact space. This can lead to the electron mean free path becoming comparable to the temperature gradient inside the loop and, therefore, to a violation of the local thermal transport approximation. In this case, the commonly used Spitzer-Harm approach is not applicable and thermal energy transport should be treated as non-local. In this regime of non-local thermal transport, suppression of heat flux and plasma preheating take place, which can strongly affect the dynamics of the plasma.
In this study, we use 1D hydrodynamic simulations to investigate how non-local thermal transport affects the thermodynamic (density-temperature) cycle of solar flares. We find that the non-local transport significantly modifies the cycle compared to the standard models of Spitzer-Harm and flux-limited local transport. In particular, during the energy release stage, the heat flux suppression leads to higher temperatures and lower densities at the loop apex. Additionally, heat fluxes result in slower chromospheric evaporation rates and, therefore, lower loop density in the case of non-local thermal transport. These effects may have observable consequences for coronal loop emission during and after flares, particularly in EUV and X-ray diagnostics.

Speaker: Sergey Belov (University of Warwick)

Basis Function Expansions in Galactic Dynamics and Evolution

Organisers: Jason Hunt, Sophia Lilleengen, Michael Petersen, Eugene Vasiliev

Half a century after their introduction, basis function expansions are seeing a renaissance in galactic dynamics and evolution owing to (1) the ability of basis function expansions to model disequilibria, critical given modern observations in the Milky Way and nearby galaxies, (2) the need for compression and analysis efficiency with the sheer size and scope of modern simulations, and (3) the accessibility of modern software frameworks (agama, EXP, gala). Work over the past decade, often led in the UK, has generated a wealth of technical improvements, enabling wider and more creative applications to analytical, numerical, and observational galactic dynamics.

Some of the earliest uses of basis function expansions in galactic dynamics described systems in analytic terms, capturing complex dynamical mechanisms such as the evolution of spiral arms. Through modern software packages, basis function expansions power rapid N-body integration of idealised systems and detailed dynamical experiments, e.g. the Milky Way-LMC interaction. More recently, basis function expansions enable detailed-yet-computationally-inexpensive representations of galaxy components in cosmological simulations, describing the shape of cosmological halos and their evolution. Further, basis function expansions can also describe images, velocity moments, and chemical fields. These additional uses of basis function expansions are still in their infancy but show significant promise for coupling theoretical and observational dynamics in the large survey era.

The session will bring together developers, practitioners, and learners for a highlight tour of recent results in galactic dynamics and evolution to set the future of basis function expansion usage and development in the UK.

09:00 Prep time

21 Basis Function Expansions: Quantifying The Things That DREAMS Are Made Of

The DaRk mattEr and Astrophysics with Machine learning and Simulations (DREAMS) project will produce thousands of Milky Way-mass, cosmological hydrodynamic zoom-in simulations that simultaneously vary both the baryonic and dark matter physics. The large scale of this dataset presents a unique opportunity to investigate the role of both the light and dark sectors in the formation and evolution of galaxies. However, analysing and providing insight into the structures within the thousands of central haloes is non-trivial, and requires the development of a common analysis framework. Basis function expansions provide a natural solution, as they are a means of producing homogeneously-derived, tailored metrics to define and quantify the structural features of the stellar, gaseous, and dark matter structure(s) in each zoom-in galaxy in DREAMS. In the context of cosmological simulations, basis function expansions have been successfully used in a number of analyses to characterize cosmological dark matter haloes and their response to perturbations, while the disks have generally received less attention. We are remedying this disparity by developing the requisite machinery for basis function expansions conditioned on disk distributions. I will outline this work and present early results of applying this methodology to cosmological stellar disks at redshift z = 0 in both warm dark matter and cold dark matter Universes in DREAMS. This talk will highlight the unique capabilities of basis function expansions in big data and cosmological simulation applications, and will conclude with a discussion of future avenues for exploration.

22 Probing the role of chaos in galaxy evolution with PECCARY and basis function expansions

Despite being well studied in N-body simulations, many challenges remain for understanding the role of chaos in the orbital evolution of isolated disc galaxies. Common methods used to identify chaos in simulations (e.g., surface of section, frequency drift, Lyapunov exponents) require long-duration sampling (on the order of a Hubble time) and/or static potentials. This poses a challenge in addressing the importance of chaos in galaxy evolution, as galaxies inherently have evolving, dynamic potentials (e.g., rotating and slowing bars). Furthermore, it is unclear whether and under what circumstances orbits have transient episodes of chaos or remain chaotic after passing through overlapping resonant regions. Expanding our toolbox in this regime will allow significant progress when addressing questions of galaxy evolution, such as how and in what cases the formation of a boxy-peanut-X (BPX) bulge feature depends on resonant sweeping or the firehose instability. We have developed PECCARY (Permutation Entropy and statistiCal Complexity Analysis for astRophYsics), a novel method for identifying chaotic, regular, and stochastic behavior in timeseries on dynamical timescales in time-dependent potentials. In this talk, I will discuss how combining PECCARY with basis function expansions (BFEs) of galaxy potentials can be used to probe the correlation between changes in the underlying potential, resonant passages, and episodes of chaos in stellar orbits. The synergy between PECCARY and BFEs represents a powerful new approach for better understanding the role of chaos in galaxy evolution.

Speaker: Soley Hyman (University of Arizona)

23 Basis function theory in galactic dynamics and beyond

I review a recent mathematical development (arxiv:2302.06944) in the theory of biorthogonal basis sets, with particular attention given to practical numerical implementation. This work introduces an algorithm, the output of which is a traditional (Clutton-Brock-style) basis set, starting from any reasonable smooth function describing the zeroth-order spherical or disc-like mass density of a chosen stellar system. There follows a discussion of the questions and research prospects raised by this line of work: first, the quest for basis functions whose underlying shape is adapted to more general galaxy geometries (discs, spheroids or ellipsoids). And second, the link between the galactic dynamicists' notion of basis function and the technique of Coulomb resolutions in computational quantum chemistry (an example of parallel development in different branches of science).

24 Time-dependent linear response theory via the matrix method

The Kalnajs matrix method is an important example of the application
of basis functions in galactic dynamics. It has been used to
determine the global response of a stellar system to perturbations in
frequency space, particularly in understanding the modes and
instabilities of stellar discs. There are, however, two shortcomings
of the method. First, it relies on the use of action-angle variables,
which greatly restricts the systems to which it can easily be
applied. Second, it is not trivial to transform from frequency space
into the temporal domain, which is natural if one wishes to
compare a linear response calculation to N-body simulations.

We show how these problems can be addressed by recasting the
linearised collisionless Boltzmann equation as an explicitly
time-dependent Volterra integral equation and applying Kalnjas' basis
function idea to that. We explain how the response kernel can
easily be constructed by direct orbit integration, avoiding
the need for angle-action variables and greatly increasing the range of problems to
which linear response theory can be applied. An important unsolved
problem is the choice of basis functions that makes these calculations
tractable in practice.

25 Dynamics of the perturbed outer Milky Way halo with basis function expansions

Recent basis function expansion models of perturbations to the Milky Way's outer halo offer new avenues to constrain the mass distribution. A key observable in this context is the reflex motion of the Milky Way disc with respect to its dark matter halo, induced by the LMC’s infall. In this work, we investigate the sensitivity of the reflex motion signal to different outer-halo profiles of the MW using a suite of basis function expansion simulations built with density-truncated NFW profiles. These profiles follow a broken power-law form, truncated beyond a characteristic break radius.

An analysis of the basis function coefficients reveals that stronger truncations (larger $\alpha$) produce a smaller dipole distortion , while the quadrupole distortion becomes more pronounced. These results highlight the limited constraining power of reflex motion amplitude alone for outer MW profile parameters. However, we also find a halo instability—whose oscillation frequency increases as $\alpha$ becomes more negative. This instability has a potentially observable signature - a radial sinusoidal pattern whose oscillation frequency increases as $\alpha$ becomes more negative.

26 The effect of the MW–LMC interaction on stellar stream populations

The recent infall of the LMC into the Milky Way (MW) has dynamical implications throughout the MW's dark matter halo, leaving an imprint on the MW stellar streams. One way to study the impact of this merger is to use the statistical properties of populations of simulated stellar streams. Using time-evolving MW-LMC simulations described by basis function expansions, I analyse how perturbations to stream properties depend on their radial distance and on-sky location, and assess whether they are driven by the direct stream-LMC interaction and/or the indirect MW halo’s response. In the outer halo, direct stream-LMC encounters increase the fraction of misaligned stream proper motions by ~25%, with the strongest effects aligning with the LMC’s current position. In the inner halo, stream perturbations are dominated by the MW dipole response, though its distinct detectability remains uncertain. Our fiducial MW-LMC model agrees with Dark Energy Survey data, and I predict the fraction of perturbed streams LSST will detect. These measurements will deepen our understanding of dark matter and LMC properties.

Speaker: Richard Brooks (University College London)

27 The distortion of the Tucana IV by the recent close passage of the Large Magellanic Cloud

The LMC has been shown to significantly affect many structures in the Milky Way, including streams and dwarfs. Recently, it has been demonstrated that the Tucana IV dwarf had a close passage (~4 kpc) with the LMC ~130 Myr ago. In this talk, I will present the results of N-body simulations of this encounter and how the LMC has distorted Tucana IV. I will show the results of N-body simulations run with Gadget-3 as well as with a recently developed restricted N-body tool. The main advantage of the restricted N-body method is that it is much faster than classical N-body.  It uses the low-order multipole expansion of the effective particle potential to compute the forces instead of considering forces from individual particles. To study the effect of the LMC on Tucana IV, I run multiple simulations sampling over the uncertainties in Tucana IV’s and the LMC’s phase space coordinates and the LMC’s mass. Interestingly, in many of these simulations, the orientations of the outskirts of Tucana IV match the observed orientation. However, the inner region of Tucana IV remains spherical, in contrast to its observed ellipticity. I will also present the results of simulations for Tucana IV initialized with an aspherical shape, i.e. a triaxial dark matter halo and stellar distribution, and compare these with observations. Looking forward, this collision between Tucana IV and the LMC, in addition to the LMC’s effect on stellar streams, will help further understand the past orbit of the LMC in our Milky Way.

Speaker: Aliaksandra Senkevich (University Of Surrey)

Unseen Astronomy: Multi-sensory approaches for research, communication and education

Organiser: James Trayford; co organisers: Nicolas Bonne, Chris Harrison, Sarah Kane, Daniel Ratliff, Rose Shepherd, Andrew Spencer

Visual approaches have long dominated in astronomy. This may not be so surprising - astronomy has produced some of the most scientifically rich and stunning imagery humanity has. However, as astronomy becomes more data intensive, with the volume and complexity (e.g. multi-dimensionality) of data exploding in recent years, traditional visual inspection methods have become increasingly untenable, with ever more ceded to complex machine-based approaches which can be difficult to interpret or verify. What's more, reliance on visuals excludes people who are blind or have low vision, and does not cater to those with different sensory preferences or learning styles. Educational research shows a multisensory approach can help reinforce learning more generally for better learning outcomes. By making use of the strengths of our diverse senses, we may develop new and powerful multi-dimensional interfaces with the data across a range of levels, and even gain new perspectives to discover ‘unknown-unknowns’ in the data.

With this session, we aim to unite a rapidly growing (but disparate) field of research into multi-modal approaches (e.g. including, sound & touch as well as vision), and how this can be used to better inspect and communicate astronomical data. Through both talks and practical sessions (divided into two parallel session blocks) we hope to investigate ways of combining approaches, while introducing attendees to these new perspectives on astronomy. In particular, a goal of the session is to move from disparate ideas towards unified approaches and practical tools that can be used in scientific and educational contexts alike.

28 STRAUSS: Sonification Tools and Resources for Analysis using Sound Synthesis

I will introduce STRAUSS, a free and open-source sonification package for Python, designed to flexibly produce sophisticated sonifications. STRAUSS is intended to integrate into data analysis, and follows cues from tools like plotting packages, so that users can produce sonification for presentation and analysis. I will discuss how we try to design a 'low-barrier, high-ceiling' tool, intending to help develop users from novice to seasoned sonifiers, with the help of bundled examples and pre-set sounds. With the v1.0 release of STRAUSS, I will also show some applications of the code across diverse data sets, producing scientific sonifications across data from diverse fields, and how we are integrating into tools to add audio functionality to existing analysis tools, such as the STScI Jdaviz to explore IFU data. Looking to the future, I'll dicuss our plans for the code and how we might use it to help expand multisenory approaches in astronomy.

• Introducing STRAUSS: https://strauss.readthedocs.io/en/latest/
• The philosophy behind the code: https://arxiv.org/abs/2311.16847
• STRAUSS @ Audio Universe: https://www.audiouniverse.org/research/strauss
• Multisensory examples with STRAUSS: https://www.youtube.com/@audiouniverse8137

29 The Tactile Universe: Communicating gravitational wave astronomy through touch and sound

For almost a decade, The Tactile Universe project has been creating multi-sensory resources to give blind and vision impaired students more options for accessing astronomy. While the project is well known for its work creating tactile images of galaxies, from 2020 - 2023 we worked with local VI students and gravitational wave research groups in England, Wales and Scotland to co-create resources focusing on the detection of, and science behind gravitational waves.

As well as creating a suite of both high tech (3D printed) and lower tech tactile resources, for the first time, the team also incorporated sonifications alongside these.

In this talk, I will showcase our new resources and discuss our experiences combining audio and tactile modes, what different but complimentary information we've been able to communicate with each and how this has been received by the VI students we've worked with, as well as the gravitational wave researchers we've trained to use these resources.

30 Using sound to expand the accessibility of solar eclipses with LightSound

Solar eclipses are some of the most spectacular astronomical events on our planet. However, they are usually framed in terms of visual phenomena, which excludes many in the blind and low-vision (BLV) community. The LightSound is a device that was developed for the 2017 North American solar eclipse to sonify the changing light brightness in real time. It has been used in several total and annular solar eclipses since then, and the LightSound Project has built and distributed almost 1000 devices through workshops in a variety of communities. Looking forward, we are working to engage with international communities to prepare for future solar eclipses and are also developing a new version of the tool that incorporates a color sensor.

Speaker: Soley Hyman (University of Arizona)

31 Beyond the Visual: the Importance of sensory Practical Wisdom for Astrophysicists and Instrument Scientists

The reliability (and nature) of human senses in rigorous scientific observations has been questioned since antiquity, and contemporary philosophy of science continues to portray astrophysicists as narrow-minded scholars, fuelled by certainty.

Drawing on visual ethnographic fieldwork with astrophysicists and instrument scientists, (microscope labs and diverse medical settings) this talks offers an alternative view of how these communities make sense of the world ‘up and out there’ beyond the visual image or spoken word. Exploring everyday scientific (and creative) embodied practices of deciding what is real, it focuses on temporary, dynamic interactions that take place through technologies and the importance of being human in the everyday world.

The applied ethnographic fieldwork is interwoven with Aristotle’s practical wisdom, Don Idhe's philosophy of technologies - and Hans-Georg Gadamer’s dialogue-as-play that moves beyond individual bodies and narrow concepts of the senses and embraces thinking through doing.

32 On the Basis of Sound: Sonifying Galaxy Images

Sonifying an image of a galaxy is not a straightforward task. There is a wealth of information encoded in the brightness of each pixel and how brightness changes as a function of location. Typically, brightness is mapped to pitch and spatial information is included via some form of panning across or around the image. While this approach successfully converts data from the visual to the aural domain, it does not succinctly summarize the salient features of a galaxy such that a listener can identify the type and structure within a few seconds, as can be possible for the same data via visual inspection. In this talk, I will present how basis function expansions provide a new avenue for sonifying galaxy data. In a two dimensional basis function expansion, the light distribution of a galaxy is condensed into a sum of weighted basis functions. Each term in the expansion corresponds to a different spatial scale, and the weight indicates the contribution of that term to the overall distribution, effectively summarizing and quantifying the structure within a galaxy. These weights can be mapped to sounds, such that a single chord can convey all of the relevant spatial and structural information in a given galaxy. I will share some examples of sonification with basis function expansions, and discuss applications of these sonifications in quantitative research. This novel application of basis function expansions advances the set of tools available in multi-sensory research and augments the data examination options that are available in morphology-based analyses.

33 Safe Space: Developing multisensory resources for disabled children

Children with complex disabilities and cognition and learning needs are often overlooked in the provision of STEM (science, technology, engineering and maths) activities. Yet working with such audiences can be hugely valuable to all involved. Even where it will not lead to a career in STEM, STEM offers a unique way to inspire young people. Creating opportunities for disabled children to love and learn from these subjects has significant individual and social impact. In addition, working with these audiences isn’t just of benefit to the children involved. The process of developing suitable resources and activities challenges us as communicators to rethink our approach and work in collaboration to develop multisensory content that can benefit children across the educational spectrum.

In this short talk, we will describe our experience of working with the Lightyear Foundation, a charity that aims to break down barriers to disabled children taking part in STEM, and a special needs school to develop multisensory workshops themed around space exploration. Our approach used virtual reality headsets, dark dens, tactile objects of different temperatures and textures, dressing-up, and edible space food to create an immersive experience that gave the children the autonomy to choose how to engage with the session. We will share our learning around working in collaboration and integrating established practices from experienced practitioners into a new context, as well as lessons learned about how using the same practical techniques can improve our wider outreach and public engagement work.

34 Astronify: An Open-Source Python Package to Sonify Lightcurves and Spectra

Astronify is an open-source Python package to sonify one-dimensional datasets, like lightcurves or spectra, using a pitch mapping technique. The primary goal is to provide sonification used to preview and analyze astronomical data for research purposes. Each data point is translated into a tone with fully customizable properties like duration, spacing, and pitch mapping parameters. In this presentation I will provide an overview of the software package, and give demonstrations of sonifications using simple datasets before showing examples with real lightcurves and spectra. Sonification offers another way to explore data, supplementing or augmenting visual techniques, since our hearing is more sensitive to changes in frequency. Sonification not only provides another tool for every scientist to use when exploring data, it also makes science more accessible by providing a powerful data exploration mechanism for those unable to use visual-only techniques.

35 A Universe of Sound: Processing NASA Data into Sonifications to Explore Participant Response

Due to its chosen detection techniques, astronomy has always been a visual science and produces some of the most beautiful images in science, engaging and awe-inspiring to many. However, scientists and communicators often overlook the need to communicate with blind and low-vision audiences who require different channels to experience this data. This study sonified NASA data of three astronomical objects and presented them to 3,184 sighted, blind, and low-vision survey participants to gauge their experience, yielding significant learning gains and positive experiential responses. Results showed that astrophysical data engaging multiple senses could establish additional avenues of trust, increase access, and promote awareness of accessibility in sighted and blind or low-vision communities. These findings underscore the urgent need to process and present information beyond images and provide new, novel methods for visual audiences to engage with science. This presentation will overview the research conducted in this work, published at Frontiers In Communication, and discuss the implications of outreach and education to the blind and low-vision community in astronomy.

The Golden Era of Gravitational Lensing: from Micro to Macro

Organiser: Maximilian von Wietersheim-Kramsta; co organisers: Aristeidis Amvrosiadis, Djuna Lize Croon, Leo Fung, Harshnoor Kaur, David Lagattuta, Samuel Lange, Gavin Leroy, Richard Massey, Nency Patel, Kai Wang

From the distortions of the images of stars due to exoplanets to the coherent warping of the relic radiation from the Big Bang, gravitational lensing (GL) is a phenomenon ingrained in the laws of gravity allowing us to probe astrophysics over a wide range of scales. Upcoming surveys, such as Euclid, Rubin LSST, SKA and Roman, will for the first time map weak GL over the whole sky from billions of sources. Simultaneously, instruments such as JWST, ALMA, ELT and HWO will observe strong GL with unprecedented resolution, while LIGO/VIRGO, LISA and IPTA can measure the impact of GL on gravitational waves. Truly, we are on the cusp of probing gravity, the nature of dark matter and the evolution of the Universe over untested regimes with unparalleled precision.

To mark this golden era in the field, we will bring together expert GL modelers, theorists, and observers to showcase and discuss their research. The session will focus on the scientific impact of GL probes: how they will inform novel theories, prepare the next generation of simulations, and improve data analysis techniques, while addressing current tensions. Through contributed talks, we will hear about a wide range of GL subfields with the aim of fostering collaboration and awareness within the field.

36 The COSMOS-Web Lens Survey (COWLS): Discovery of >100 high redshift strong lenses in contiguous JWST imaging

I present the COSMOS-Web Lens Survey (COWLS), a groundbreaking sample of over 100 strong lens candidates identified within the $0.54$deg$^2$ COSMOS-Web survey using high-resolution James Webb Space Telescope (JWST} imaging across four wavebands. Through two rounds of visual inspection and lens modeling, more than 100 candidates were classified as ‘high confidence’ or ‘likely’ by at least $50\%$ of inspectors.

The COWLS sample offers unique opportunities for scientific exploration, featuring: (i) magnified source galaxies spanning redshifts from $z \sim 0.1$ to $z \sim 9$, including those extending into the epoch of reionization; (ii) the highest-redshift lens galaxies known, advancing galaxy density profile evolution studies beyond $z \sim 2$; (iii) a contiguous $0.54$deg$^2$ region ideal for joint strong and weak lensing analyses; and (iv) lenses exhibiting source emission ray-traced near lens galaxy centers, enabling detailed studies of supermassive black holes and dust absorption. I present the first public COWLS data release and outline the next steps on how COWLS can change our understanding of galaxies and cosmology.

37 Line-of-sight shear: progress and challenges

In this talk I will review the concept of the line-of-sight (LOS) shear, a model for external shear in strong lensing that is theoretically free from degeneracies with lens model parameters. Measurements of the LOS shear will provide new, independent constraints on cosmological parameters such as $\sigma_8$ via a cross-correlation with traditional weak lensing probes. I will present a mock-based proof-of-concept that this observable is measurable from strong lenses, along with the first measurements of LOS shear from the SLACS strong lens sample. I will further show estimates for the expected cosmological signal of LOS shear measured in Euclid, and a forecast for constraints achievable on $\sigma_8$ from the full Euclid Wide Survey.

Based on 2210.07210, 2405.12091, 2501.16292 and work in prep.

38 Probing Dark Matter Substructures with Free-Form Modelling: A Case Study of the `Jackpot' Strong Lens

Characterizing the population and internal structure of sub-galactic haloes is critical for constraining the nature of dark matter. These haloes can be detected near galaxies that act as strong gravitational lenses with extended arcs, as they perturb the shapes of the arcs. However, this method is subject to false-positive detections and systematic uncertainties: particularly degeneracies between an individual halo and larger-scale asymmetries in the distribution of lens mass. We present a new free-form lens modelling code, developed within the framework of the open-source software \texttt{PyAutoLens}, to address these challenges. Our method models mass perturbations that cannot be captured by parametric models as pixelated potential corrections and suppresses unphysical solutions via a Mat\'ern regularisation scheme that is inspired by Gaussian process regression. This approach enables the recovery of diverse mass perturbations, including subhaloes, line-of-sight haloes, external shear, and multipole components that represent the complex angular mass distribution of the lens galaxy, such as boxiness/diskiness. Additionally, our fully Bayesian framework objectively infers hyperparameters associated with the regularisation of pixelated sources and potential corrections, eliminating the need for manual fine-tuning. By applying our code to the well-known `Jackpot' lens system, SLACS0946+1006, we robustly detect a highly concentrated subhalo that challenges the standard cold dark matter model. This study represents the first attempt to independently measure the structure of a subhalo using a fully free-form approach.

Speaker: Xiaoyue Cao (University of Chinese Academy of Sciences)

39 Super-Concentration or Unaccounted Light? Unveiling the True Nature of the Subhalo in SDSSJ0946+1006

Recent strong lensing analyses have suggested that the dark matter subhalo detected in SDSSJ0946+1006 has an extremely high concentration, which is difficult to reconcile with predictions from the standard cold dark matter (CDM) model. However, previous studies did not properly account for the possible contribution of light from a galaxy embedded within the subhalo, if such a galaxy exists. Using a more advanced model that fully incorporates the satellite galaxy’s light, we constrain the subhalo’s mass profile and find it to be fully consistent with CDM predictions. This also represents the first strong lensing-based measurement of a dwarf satellite's light and mass, marking a significant step forward in the study of dwarf satellites at cosmological distances.

40 Detecting subhalos with very steep inner-density profiles using strong gravitational lensing

This work investigates how the lensing signature and detectability of dark matter subhalos in mock HST and Euclid-like strong lensing observations depends on the subhalo's radial density profile, especially with regards to the inner power-law slope, $\beta$. The inner region of a subhalo's density distribution is particularly sensitive to dark matter microphysics, with alternative dark matter models leading to both cored ($\beta \sim 0.0$) and very steep inner density profiles ($\beta > 2.0$). We demonstrate that the minimum-mass subhalo detectable along the Einstein ring of a system is strongly dependent on $\beta$. We find that subhalos with $\beta \sim 2.2$ (resembling core-collapsed subhalos that can arise from dark matter self interactions) can be detected down to halo masses approximately an order-of-magnitude lower than their NFW counterparts. We also demonstrate how accurately one can infer $\beta$ and distinguish cored versus steep inner density slopes from lensing observations. The results of this work highlight how strong lensing subhalo detections, or lack-thereof, may aid in dark matter constraints, particularly pertaining to models such as SIDM, which predict the existence of subhalos with very steep inner density profiles.

41 Group-Scale Lenses with JWST: Probing Magnified High-Redshift Galaxies And Extending Cosmological Distance Measurements

The James Webb Space Telescope (JWST) has opened a new frontier in strong gravitational lensing by providing the resolution and depth necessary to identify some of the most distant lenses ever discovered. Among these are group-scale lenses, systems of approximately 2–10 galaxies that bridge the gap between galaxy- and cluster-scale lenses. These systems offer magnifications up to ten times higher than galaxy-scale lenses ($\mu\sim 50$) whilst maintaining sufficiently simple mass models that allow for the ability to reconstruct the unlensed source morphology. We modelled a sample of five JWST group-scale lenses identified in the COSMOS-Web survey, leveraging JWST’s multi-band imaging to perform high-precision lens modelling. Our lens model accounts for the contribution of the 4-10 galaxies per system, whose contribution to the lens is key to reconstructing the source’s detailed morphology on an adaptive Voronoi mesh. Notably, we identified a spectroscopically confirmed source at $z=4.99$, which is HST-dark, allowing us to reconstruct its structure which provides an unprecedented view of this galaxy class emerging as key to high redshift galaxy evolution. The sample also includes two double-source plane lens candidates, one of which features the $z=4.99$ source. These systems therefore motivate an exploration of how JWST group-scale lenses can inform cosmological parameter inference, given they could extend the angular diameter distance redshift range–critical to cosmology–over a much more significant range than achievable with galaxy-scale lenses.

Speaker: Niek Wielders

The Interplay between Technology and Astronomy

Organisers: NAZIM ALI BHARMAL, Meryem Kubra DAG, DEBORAH MALONE

This parallel session focuses on the dynamic interplay between astronomy and technology, examining how astronomical innovations influence fields beyond space sciences and how advancements in other disciplines contribute to the progress of astronomy. The session will explore the transformative impacts of astronomical technologies on engineering, medicine, environmental science, data analytics, and social systems.

Key topics may include the application of space telescope imaging technologies in medical devices, the adaptation of adaptive optics systems for environmental monitoring. Additionally, the integration of astronomical data analysis techniques into social sciences and other interdisciplinary interactions will be discussed. By bringing together researchers and practitioners from diverse fields, this session aims to highlight the value of interdisciplinary collaboration and the broader societal impact of astronomical innovations.

Through these discussions, the session seeks to strengthen the connections between astronomy and other disciplines, emphasizing the scientific and societal importance of technologies originating from space sciences.

09:00 Prep time

42 Use of solid fused silica metalon as a wavelength calibrator for high-resolution optical EXOhSPEC spectrograph

​Wavelength calibration establishes a physical scale by mapping absolute wavelengths onto the pixel positions of the detector of any astronomical spectrographs. Precise wavelength calibration is crucial for measuring physical quantities, for example, radial velocities via high-resolution spectrographs. In general, hollow-cathode lamps (e.g. ThAr), Fabry-Perot etalons, and laser frequency combs offer wavelength calibration for high-resolution spectrographs. However, due to their various limitations as calibrators, investigations of any cost-effective alternative methods remain of prime interest. In this presentation, I shall discuss the feasibility of two commercially available solid fused silica etalons with broadband metallic coatings, metalons having different cavity spacing (free spectral range of 1/cm and 0.5/cm) in the laboratory. We studied the behaviour of metalons from theoretical derivation and experimental data and found that theoretical predictions corroborated with experimental measurements. The temperature of the metalon system was controlled with active temperature control methodology using a controlled loop feedback system and an off-the-shelf dewar flask and a temperature stability of 0.8 mK was achieved. We measured radial-velocity drift using standard software, e.g., TERRA and SERVAL and our result demonstrated that metalon is capable of providing higher signal-to-noise calibration and better nightly drift measurement relative to ThAr in the wavelength range between 470 nm and 780 nm. Although a similar result was found earlier from etalons and the metalon solution lacks the efficiency of an etalon, the metalon offers a cost-effective broadband solution free from the ageing of dielectric mirror coatings. Nonetheless, long-term monitoring is required to understand the metalon performance in detail.

Speaker: Supriyo Ghosh (University of Hertfordshire)

43 Lessons learned from WEAVE

The integration and commissioning of WEAVE has been an extended process marred by Covid, a Shipping Crisis, Volcano and Forest Fires, as well as the usual issues one expects with a complex instrument. Aside from external events there are some useful lessons from the process that I will relate, as these have relatively broad application and should be retained within the community for future reference.

Speaker: Gavin Dalton (University of Oxford/RALSpace)

44 The Role of Artificial Intelligence in Revolutionizing Modern Astronomy

The field of astronomy is undergoing a transformative era, driven by the integration of artificial intelligence (AI) into its methodologies and practices. In this talk, I will explore how AI is revolutionizing the study of the cosmos by enabling astronomers to process vast datasets, uncover hidden patterns, and accelerate discoveries. From identifying exoplanets and classifying galaxies to detecting gravitational waves and monitoring transient celestial phenomena, AI has become an indispensable tool in addressing some of the most complex challenges in astronomy.
I will discuss key applications of machine learning and neural networks in analysing astronomical data, predicting celestial events, and enhancing imaging techniques for phenomena such as black holes. Additionally, I will address the challenges posed by AI, including issues of model interpretability, biases, and reliance on simulated data. Looking ahead, I will highlight emerging opportunities for AI in large-scale projects like the Vera Rubin Observatory and the democratization of astronomical research through open-access AI tools.
This session aims to inspire researchers and enthusiasts to embrace AI as a powerful ally in unravelling the mysteries of the universe while fostering critical discussions about its limitations and ethical implications. The session aims to explore how AI is not only reshaping our understanding of the cosmos but also redefining the future of astronomy itself.

Speaker: Fawada Qaiser (Durham University)

45 Applications of CMB receiver technology

Simons Observatory UK is a state-of-the-art cosmic microwave background observatory with hardware currently under development at various institutions in the UK, and telescope infrastructure being assembled in the Atacama Desert in Chile. In this talk I will outline the SO:UK receivers and show how some of the microwave, superconducting and cryogenic technologies developed for CMB observatories can be applied beyond radio astronomy. Some of the areas that I will discuss include: dark matter detection, quantum computing and quantum sensing, and medical imaging.

Speaker: Mark McCulloch (The University of Manchester)

46 Insight on forecasting techniques from their application to the solar wind

One common feature of many fields is the necessity to forecast the temporal evolution of signals and the question is always more challenging when the signal is irregular and multiscale. For instance, we can find forecasting the temperature variation or the localisation of rainy clouds in meteorology, the daily or monthly stock exchange for finance applications, tiny variations in electrocardiograms to diagnose cardiac ailments, or forecasting the solar, solar wind, and geomagnetic activity to prevent threats to our society from space weather.
The Analogue Ensemble technique originates from Lorentz’s idea, to forecast the weather, that we can forecast the future evolution by finding similar occurrences of the present behaviour in the past and by considering the progression of these occurrences. This idea leads to an ensemble of forecasts. We use this technique to forecast the magnetic and velocity field of the solar wind for Space Weather applications. By comparing the obtained forecasts to climatology (long-term average), persistence (future constant progression of the present state), and recurrence (cyclic occurrence), we have demonstrated that the fluctuations of these quantities can be well estimated with the AnEn method. We can describe, scale by scale, the fluctuations of a signal with a spectrum in the Fourier frequency space. As a multiscale system, the spectra of solar wind quantities span a broad range of frequencies and should be reflected in the forecast. We propose novel ensemble-reduction and diagnostics techniques to preserve and measure the spectral performance of the ensemble forecast.

Speaker: Dr Pauline Simon (Department of Physics and Astronomy, Queen Mary University of London, London, UK)

10:30 Coffee Break

11:00 Opening Ceremony

Plenaries 1 - Monday

47 The tumultuous life of early galaxies: bursty star formation and the build-up of disks

The formation of the first galaxies was anything but boring—intense bursts of star formation, turbulent mergers, and the gradual emergence of structure all played a role in shaping the universe as we see it today. In this talk, I will explore the latest breakthroughs in our understanding of early galaxy evolution, bridging state-of-the-art theoretical models with groundbreaking observations from the James Webb Space Telescope (JWST). Using insights from the THESAN-zoom cosmological simulations, I will examine how the first galaxies regulated their star formation, evolved along the star-forming main sequence, and grew in size in the first billion year of cosmic time. Connecting these predictions with new JWST data from the JADES survey, I will highlight the remarkable diversity of galaxies at cosmic dawn (redshift z>10), where intense bursts of star formation and black hole activity were common. I will also discuss how galaxy mergers influenced their evolution and how disk-like structures began to emerge during the Epoch of Reionization (z=4−10). By linking theoretical and observational constraints, this talk will provide a comprehensive picture of how galaxies took shape in the early universe, shedding light on the forces that governed their tumultuous beginnings.

Speaker: Sandro Tacchella (Kavli Institute for Cosmology, University of Cambridge)

12:05 Monday Plenary 2 - TBA

12:45 IOP Drinks Reception

IOP stall, TLC top floor

12:45 Lunch

UK Solar Physics Business Session

Organisers: Natasha Jeffrey, Marianna Korsos, Matthew Lennard, Karen Meyer, Ryan Milligan, Rahul Sharma, Suzana Silva, Peter Wyper

In this session, we will host the UK Solar Physics (UKSP) business session, which is a place where the UKSP Council will provide updates on our initiatives and projected plans to the solar community. We will have invited presentations from representatives on key funding councils (for example, the Solar System Advisory Panel). We will have an open forum for discussing key concerns within the community, including, but not limited to, access to funding opportunities, doctoral student support, space and ground-based instrumentation, and community meetings/conferences. We welcome input and participation across the breadth of the community and across all career stages.

Moon Palace: training physics student ambassadors in arts-based engagement methods

Organiser: Lorraine Coghill; co organisers: Kerry Harker, Eliza Hunt, Claire Irving, Ged Matthews, Erin McNeill

Moon Palace, an artwork and mobile observatory by Heather Peak and Ivan Morison, brings together arts organisation, the East Leeds Project, and Physics departments at the University of Leeds, Durham University, University of Hertfordshire, and Queen Mary University of London.

This collaborative project, funded by The Ogden Trust, aims to empower undergraduate and postgraduate student ambassadors with interdisciplinary skills, fostering their growth as leaders while enhancing access to astronomy and culture for underserved communities. By bringing the mobile observatory which is also an artwork directly to local neighbourhoods, we aim to deepen relationships between universities and their local communities.

A key component of this initiative is evaluating the impact of arts-science outreach collaboration on our physics ambassadors. The evaluation will explore how this unique blend of disciplines enhances the ambassadors’ creativity, confidence, and engagement with diverse groups, including artists and community partners. We are committed to understanding the transformative experiences of our ambassadors and how these experiences contribute to their personal and professional development.

The Moon Palace itself will be present at NAM and all are invited to experience its unique atmosphere (times tbc). This interactive session will offer a taster of the training programme offered to the Ambassadors, allowing participants to explore the background, methods and practicalities of using arts-based methods for engaging with communities in astronomy, and consider how these could be used in their own settings.

Workshop: How to build an Instrument for Astronomers

Organiser: Deborah Malone; co organiser: Meryem Dag, Emily Ronson

This session is to facilitate the communication between Astronomy and Instrumentation Early Career Researchers as a fun activity which encourages groups of participants to design a new instrument together from scratch. First, the group is given a brief introduction (~5 minutes) on how instruments are built, including the kinds of criteria that are important to define. Then, the groups (3-4 people) can be given a random observation target, or decide for themselves, along with keywords to help in designing the instrument, and work together for ~20 mins to determine what kind of instrument they would need to observe it with, the size of the telescope, how long they need to observe it for, and what kind of adaptive optics they would need to use. Is it an exoplanet? Does it need high-contrast imaging? Is it a high red shift galaxy? Does it need to be observed with an extremely large telescope? Perhaps it’s a fast-moving comet that’s very close to the sun!

At the end, each group has two minutes to present their concept instrument for their chosen observation target, and a panel of peers will give out prizes for best pitch, along with a few other fun awards.

Astronomers and Instrumentation Scientists must work together to develop the next generation of Telescopes, and it is extremely important to understand the needs of each group to successfully design and build the instruments that will form part of the telescopes.

14:00 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

14:15 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

The ultimate fate of multi-phase gas in galaxies: from giant molecular clouds to the virial radius

Organisers: Bronwyn Reichardt Chu, Thomas Rintoul; co organisers: Alex Cameron, Fred Jennings, Seoyoung Lyla Jung, Hengxing Pan, Martin Rey, Tianyi Yang

The baryon cycle regulates star formation and shapes galaxies across cosmic time. Gas is accreted onto galaxies from the circumgalactic medium (CGM), used as fuel for star formation, stirred up by young massive stars, and expelled out of galaxies by stellar feedback processes, contributing back to the CGM where it can cool and reaccrete. Characterising multiphase gas - its structure and dynamics, the impact of stellar feedback, and its interplay with local, galaxy and cluster scale environments - is a key problem of modern galaxy formation.

There are many challenges in both observing and simulating the full baryon cycle. Gas is impacted over a vast range of scales, from individual massive star winds, ionising radiation and explosions (~pc) to star formation-driven galaxy-scale outflows contributing to the CGM (~100s kpc) and IGM (~Mpc). In addition, gas within and surrounding galaxies is intrinsically multiphase, spanning more than 8 orders of magnitude in both density and temperature. This requires the combination of multi-wavelength observational data and high-resolution simulations on a range of scales to form an understanding of the role of gas within galaxies.

This session seeks to bridge the gap between observers and simulators to discuss recent progress towards tackling these challenges, solidifying our current understanding of questions such as “How can we constrain the physics driving the baryon cycle?”; “What effect does environment have on the multiphase baryon cycle?”; “How can we connect the effects of feedback across scales?”; and “How can we best use numerical simulations to interpret and inform observations of multi-phase gas in and around galaxies (and vice versa)?”

14:15 Prep time

48 Modified IGM Enrichment as a Constraint on the Mass-Loading of Outflows from Low-mass Galaxies

Highly mass-loaded outflows from low-mass galaxies are a well-established consequence of ubiquitous implementation of energetic feedback prescriptions into hydrodynamical simulations and are produced by the smallest of galaxies in simulations such as EAGLE and TNG, resulting in mass loadings ($\eta$) between 10 and 100. However the observational literature lacks consensus on the presence of highly mass-loaded outflows from galaxies of similar masses, possibly in part due to the difficult nature of measuring this by observational means. Measurements from EAGLE and TNG disagree with some of the recent observational studies by up to several orders of magnitude, with a recent study (Marasco+23) identifying values in the region of $\eta=0.02$.

Low-mass galaxies are touted as being responsible for the bulk of IGM enrichment (Wiersma+10; Booth+12) as observed through QSO absorption lines. Using Aguirre+02’s Pixel Optical Depth (POD) method (see also Turner+14), Turner+16 produce optical depth statistics from EAGLE to show the relation between metal enrichment and environmental gas density.

We analyse the impact of selectively removing metals from EAGLE according to their source galaxy mass by considering the impact on said statistical relation. By doing so, we can identify whether the lowest mass galaxies contribute significantly to IGM enrichment and whether such galaxies require highly mass-loaded outflows to support this enrichment.

I will be presenting results obtained from both analytical and POD analysis (the latter producing an observable relation) to identify the galaxies responsible for IGM metal enrichment and additionally a commentary on how this analysis can be extended to newer simulations.

Speaker: Mr Christopher Rowe (Astrophysics Research Institute, Liverpool John Moores University)

49 The MUSE Ultra-Deep Field: Tracing the baryon cycle through low-mass galaxies since cosmic noon

The MUSE Ultra-Deep Field (MUDF) is the deepest field observed with MUSE to-date, with over 140h of observations covering a 2’x2’ field centered on a pair of z~3 quasars. This is accompanied by datasets from other instruments including ALMA, HAWK-I, UVES, and XMM-Newton, as well as multi-band HST imaging and the deepest ever WFC3 grism survey. We measure morphologies, stellar masses, and star-formation rates (SFRs) for over 400 galaxies with spectroscopic redshifts across a range of environments. We also measure metallicities for many of these galaxies, alongside hundreds of metal absorption features arising from the circumgalactic and intergalactic medium (CGM and IGM) along the two quasar sightlines. Combined, these data provide unprecedented insight into the properties of low-mass galaxies since cosmic noon and the cycle of metals between galaxies and their surroundings.

I will discuss several results enabled by this remarkable dataset. First, we extend measurements of the star-forming main sequence and mass-metallicity relation (MZR) to low stellar masses of 10^7 solar and star-formation rates ~1 dex lower than previous works, finding that the low-mass slope of the MZR depends on SFR but does not flatten at our lowest masses. Using auroral emission lines, we also confirm that strong-line calibrations can reliably be used to measure metallicities out to redshifts of at least z~2.5. Second, we find more CGM absorption along the major and minor axis of star-forming galaxies, indicating that star formation is an important driver of the cycle of metals through low-mass galaxies since cosmic noon.

Speaker: Alexander Beckett (Space Telescope Science Institute)

50 The Role of Magnetic Fields in the Ram Pressure Stripping of Satellite Galaxies in the Circumgalactic Medium

Ram Pressure Stripping of satellite galaxies is an important mechanism for enriching the Circumgalactic Medium (CGM). Simulations show that satellites contribute a non-negligible quantity of metals to the CGM, inducing cooling and enhancing accretion onto the central galaxy. Simulations without metal-line cooling in the CGM show systematically lower stellar masses.
While ram pressure stripping has been studied extensively using hydrodynamical simulations, little work has been done to explore the effects that magnetic fields have on ram pressure stripping.
Magnetic fields are known to be present throughout the CGM and in the tails of ram pressure stripped cluster galaxies - known as jellyfish galaxies.
In this talk, I will discuss our work exploring the effects of magnetic fields on ram pressure stripping and the subsequent evolution of the stripped material.
We do this using high resolution cosmological zoom-in simulations of massive galaxy haloes. We use the Auriga galaxy formation model and the moving-mesh, magneto-hydrodynamics code, AREPO.
For a suite of simulations with and without magnetic fields, we analyse mass loss rates for a sample of satellite galaxies, and study the evolution of their stripped tails. We determine the origin of the cool gas in the tail and explore the mechanisms behind differences in the evolution of the tail.
We conclude that for massive satellites in the CGM, magnetic fields can severely limit the rate of ram pressure stripping and hamper interactions between the stripped tail and the host CGM through magnetic draping and suppression of fluid instabilities.

Speaker: Thomas Rintoul (Cardiff University / Prifysgol Caerdydd)

51 Simulating the multiphase CGM: turbulence, cloud kinematics and observational signatures

Most of a galaxy's gas resides in its halo's atmosphere, known as the circumgalactic medium (CGM). Like our own atmosphere, the CGM consists of a hotter, volume-filling component and cooler clouds that can 'rain' onto the galaxy's disc and fuel the formation of new stars. However, simulating the cooler clouds and the entire atmosphere simultaneously poses significant computational challenges, since the short cooling length of the densest clouds demands high spatial resolution.

To address this challenge, we conduct a suite of high-resolution magnetohydrodynamic simulations, modeling the CGM as turbulent boxes spanning 1-10 kpc, where the smaller boxes resolve the cooling length better. By systematically varying the box size, we explore two distinct scenarios: constant turbulent heating rate (which maintains the energy cascade) and fixed cooling-to-mixing time ratio, a critical parameter governing cold cloud survival. Our analysis focuses on the survival of cold clouds and their kinematics, distinguishing between internal motions and group velocities within the hot medium and comparing them against the kinematics of the hot phase. We validate our findings against observational line width-size relations for cold clouds and generate synthetic column densities for key ions (MgII, SiIV, OVI), enabling direct comparison with quasar absorption line data. Additionally, we explore alternative turbulence diagnostics, including velocity and density power spectra, comparing their characteristics in single-phase and multiphase turbulence regimes. This analysis has important implications for understanding the scattering of Fast Radio Burst signals in the multiphase CGM, where AU-scale density fluctuations within the cold clouds could play an important role.

Speaker: Rajsekhar Mohapatra (Princeton University)

52 The cool CGM mapping of individual galaxies

Galaxies are surrounded by diffuse ionized gas, which is often called the circumgalactic medium (CGM) and is the least understood part of galactic ecosystems. The CGM harbors more than 80% of the total baryons in a galaxy, is both the reservoir of gas for subsequent star formation and the depository of chemically processed gas, energy, and angular momentum from feedback, however, we do not yet have a complete map of the CGM for any galaxy. The recent detection of optical emission lines from the CGM in combined, large samples of low-redshift, normal galaxies hints at the potential to map the cool (~10^4 K) CGM in individual local galaxies. Using the integral field unit (IFU) spectra, we present the first source-blind, wide-redshift-range (z ~ 0-5) narrow-band imaging survey for CGM emission. We present >30 kpc wide [O II]λλ3727,3729, Hβ, [O III]λ5007, Hα, [N II]λ6584 emission maps tracing the CGM of a low-mass starburst galaxy (M_*~10^8.6 M_⨀) at a redshift of 0.04723. We also present a 130 kpc wide [O II]λλ3727,3729 feature revealing an interaction between a galaxy pair at z=1.248. The Hα velocity field for the low-mass galaxy suggests that the CGM is more chaotic or turbulent than the galaxy disk, while that for the interacting galaxies shows large-scale coherent motions. We show that deep, integral field spectroscopy can be used to map the CGM of local, normal galaxies and to uncover examples of higher redshift, more dramatic examples of the CGM.

Speaker: Huanian Zhang (Huazhong University of Science and Technology)

53 MgII Absorbers in the CGM of Post-Starburst Galaxies

The Circumgalactic Medium (CGM) plays a vital role in galaxy evolution, yet its connection to cool gas remains poorly understood. We show that post-starburst galaxies, which recently underwent rapid star formation quenching, exhibit distinct CGM properties. Using ~850,000 quasar sightlines from the SDSS CMASS sample, we measure the stacked MgII equivalent width as a function of impact parameter for massive galaxies (>$10^{11} M_⊙$).
Consistent with previous results, we find that MgII absorption decreases with distance, indicating a decline in cool gas abundance. At ~1 Mpc, MgII levels converge across galaxy types, marking a transition from the CGM to the intergalactic medium. Post-starburst galaxies show significantly enhanced MgII absorption compared to star-forming and non-star-forming galaxies. This unique CGM signature in post-starburst galaxies potentially links to outflows observed in their interstellar medium, or alternatively to the impact on their CGM of a significant recent disruption, such as caused by galaxy mergers.

Speaker: Zoe Harvey (University of St Andrews)

15:24 Discussion

Mitigation and the Underbelly: dark and quiet skies and the darker side of satellites

Organisers: Fionagh Thomson, Marieta Valdivia Lefort; co organisers: Leah-Nani Alconcel, Martin Barstow, Lily Beesley, James Blake, Dan Cziczo, Federico Di Vruno, Robert Massey, Lesley Jane Smith

Since 2019, the call to protect Dark and Quiet Skies has gathered significant attention, as the deployment of mega-constellations into low-earth orbit (LEO) escalates - and launch to Very Low Orbit is planned. Satellite launch will only increase as will the reflective sunlight pollution from the orbiting metallic bodies and the noise interference from their broadband transmissions that negatively impacts optical and radio observations, respectively. The astronomy community has made progress, including extensive negotiations with satellite operators. But we need new ideas, collaborations and strategies to move this complex and challenging issue from the sidelines into the spotlight for government and industry.

This session invites abstracts in two different categories on this topic:

(1) Improving technical and legal mitigation strategies
The astronomy community has worked to raise awareness, including partnering with lawyers and social scientists to develop a more holistic approach to find solutions. But more research and collaborations are needed to persuade governments and industry to define mitigation strategies at both technical and regulatory levels. This session aims to continue exploring mitigation strategies for the impact of large satellite constellations in astronomy by presenting more evidence for stricter technical requirements applicable to the design and authorisation of space technologies. We welcome contributions ranging from scientific research and simulations showing data for technical improvements, to suggestions for improvement of regulatory frameworks at both the international and national levels.

(2) Will megaconstellations deliver all their heavenly promises to Earth?
New commercially-led Space wields significant economic and geopolitical power over astronomy. Private venture capitalists and public space agencies project vast economic return on investments and increased jobs. LEO and GEO are protected by international regulations. New Space is painted as a benevolent ‘ecosystem’ serving humanity on Earth, providing important scientific data. At all costs, orbits must be protected. In this global power contest, astronomy is often placed on the sidelines as a non-commercial beautiful scientific endeavour that (when push comes to shove) is secondary to the benefits of New space. But are these promises fact or fiction? This section invites abstracts on the following questions: Is everything launched into LEO/GEO linked to worthwhile scientific or humanitarian endeavours? Is the space sustainability movement designed to benefit both New Space and Astronomy? Are there alternative options to LEO satellites for launching/deploying payloads?

Timetable_#105.csv

14:15 Welcome remarks

54 Mitigating Reflectance: Simulating the Orbital Dependence of Satellite Brightness

The brightness of satellites as observed from Earth varies significantly with orbital parameters and solar angle, with the brightest satellites leaving trails across astronomical images. This work explores how a satellite's altitude, inclination and structure, as well as the observer's position, affects the apparent brightness of the satellite. Using a rudimentary ray-tracing model that incorporates these parameters, we discuss the various orbital regions and local times of day when satellite brightness is minimised for astronomical observations.

55 A mitigation tool to forecast satellite passes and brightness for optical telescopes worldwide

Our skies are fundamentally changing as the satellite constellation population rapidly increases. Sun-reflected luminosity from a large number of satellites can produce bright streaks on astronomical observations and impact the pristine appearance of the night sky. Models and data for satellite brightness are being developed to enable mitigation, active avoidance, or use in compliance checks.

The IAU’s Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) is addressing these challenges through a recent U.S. NSF award. The collaborative SWIFT-SAT grant between NOIRLab and U. Illinois brings together a consortium of experts to quantify and ultimately mitigate impacts of satellite streaks on optical observations. By leveraging high accuracy, precise positions of space objects’ orbits from Aerospace Corporation, a network of observers, and novel brightness modeling from U. California Davis, software solutions for forecasting satellite passes and ultimately predicting satellite brightnesses are being produced. The resulting publicly-available web-based service is called SatChecker.

SatChecker is potentially usable by both satellite operators and observatories worldwide, and in the verification and validation of brightness mitigation measures taken by satellite operators. ​​As a test, the research will substantially advance our understanding of the impact of the variation in brightness along satellite streaks on the discovery and characterization of solar system objects and on the rate of false positives in transient object detection on the Rubin Observatory.

The project is a primary means by which IAU CPS is leveraging its truly international constituency to address this urgent global issue.

56 Mitigating Satellite Light Pollution with Vantablack Coatings: A Collaborative Approach to Protecting Astronomy

The rapid expansion of low Earth orbit (LEO) satellite mega-constellations, such as Starlink and OneWeb, has transformed global connectivity but poses a challenge to ground-based optical astronomy. Satellite reflections disrupt imaging pipelines, degrade signal-to-noise ratios, and compromise the scientific output of major observatories, including the Vera C. Rubin Observatory, which is expected to detect satellite trails in a significant fraction of its wide-field observations. Additionally, small space objects contribute approximately 10% to the natural sky brightness, while planned mega-constellations are projected to increase sky brightness by up to 1% in the worst-affected regions through discrete contamination.

With thousands more satellites planned for launch over the next decade, the requirement for mitigation strategies is growing. In this context, we present an interdisciplinary collaboration between astronomers at the University of Surrey, and materials scientists at Surrey Nanosystems, aimed at reducing satellite brightness with novel surface treatments. We report on the qualification of Vantablack® 310, a low-reflectance, space-grade coating, for application on a student-led satellite mission. The coating has been engineered to withstand the harsh conditions of LEO while significantly reducing visual signatures across a range of viewing angles.

We discuss the expected impact of Vantablack® 310 on satellite photometric profiles, its integration into standard satellite design, and the broader implications for astronomy–satellite coordination frameworks. By addressing the increasing threat of satellite interference, this work seeks to harmonize the benefits of global connectivity with the protection of astronomical research and the natural night sky.

57 Satellite constellations and radio astronomy - clarifications on regulatory status of radio astronomy and current mitigations

Radio astronomy is seeing an exponential increase of satellites in LEO, producing strong signals to communicate with Earth and also unintentional electromagnetic radiation (UEMR) as noise produced by the electronics onboard. These are two distinct effects that need careful consideration: intentional transmissions from satellites are well regulated through the International Telecommunication Union, UEMR is a new effect that lacks an international recognition in the regulatory framework.
This talk will explore these two effects and in particular the existing regulatory framework for intentional emissions. I will then discuss the steps being undertaken to protect the Radio Astronomy Service (RAS) at the ITU towards the World Radiocommunication Conference and the technique of boresight avoidance as a collaboration with satellite operators.

58 ESA’s dark and quiet skies requirements and technology developments

The dark and quiet sky must be protected to avoid deteriorating astronomical research but also for its cultural and societal significance. Consequently, the satellite brightness
characterisation and reduction are covered by the new Zero Debris Charter and ESA's Zero Debris space debris mitigation requirements, and accordingly addressed in the Zero Debris Technology booklet.

ESA is implementing approaches to understand the impact of its current and future missions, and to lead in responsible spacecraft design and operations that minimise the impact.

New materials, manufacturing processes, operational modes, coordination means, and compliance assessment and verification methods need to be developed to reduce the optical and RF signature and allow building dark and quiet spacecrafts. Specific challenges in the verification of some requirements are highlighted.

Currently running and planned activities in ESA’s Space Safety and Technology Development programme will be presented, e.g. brightness characterisation from ground, in laboratory facilities, and using simulation software.

59 IAU CPS: Improving our understanding of satellite constellations and engagement with industry

The IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) was formed in response to ever-increasing numbers of satellites, particularly in low-Earth orbit constellations. It has four hubs, including SatHub, Policy, Community Engagement, and Industry & Technology hubs. Of these, SatHub focuses on observation campaigns, brightness data analysis, and software curation to improve our understanding of the impact of satellite constellations on observers worldwide. SatHub works with astronomers and sky observers across all wavelengths. SatHub is developing online services to simplify satellite constellation mitigation in astronomical observation planning, such as a satellite pass prediction tool, SatChecker, and the Satellite Constellation Observation REpository (SCORE), a database of measured satellite brightnesses.

I will briefly introduce the IAU CPS, its main areas of work, accomplishments and ongoing efforts, along with its activities to protect Dark and Quiet Skies at the International Telecommunication Union (ITU) and at the UN Committee on the Peaceful Uses of Outer Space (COPUOS). I will share what SatHub has learnt so far about the effectiveness of mitigations through its observing campaigns and tools like SCORE, and look to the future for what may be coming next with the launch of future satellite constellations.

14:55 Q&As

60 Part 2 Panel (audience Q&A): Will Space Deliver all it’s Earth-Born Promises?

Will megaconstellations/Space deliver all their heavenly promises to Earth?. (with audience Q&A).
New commercially-led Space wields significant economic and geopolitical power over astronomy. Private venture capitalists and public space agencies project vast economic return on investments and increased jobs. LEO and GEO are protected by international regulations.

New Space is painted as a benevolent ‘ecosystem’ serving humanity on Earth, providing important scientific data. At all costs, orbits must be protected. In this global power contest, astronomy is often placed on the sidelines as a non-commercial beautiful scientific endeavour that (when push comes to shove) is secondary to the benefits of New space. But are these promises fact or fiction? This panellists will answer challenging questions such as:
- Is everything launched into LEO/GEO linked to worthwhile scientific or humanitarian endeavours?
- Is the space sustainability movement designed to benefit both New Space and Astronomy?
- Are there alternative options to LEO satellites for launching/deploying payloads?

15:35 Q&As

print('Hello Future'): Developing Next Generation Astronomical Codes

Organisers: Sarah Johnston, Alastair Basden, Carlton Baugh, Sownak Bose

Modern computing capabilities are allowing us to delve further and learn more about our universe. Ongoing developments to simulations allow us to model larger problems and do so in greater detail than ever before, and our instrumentation advancements are leading to telescopes which produce massive amounts of data. To accommodate this, astronomy codes are relying more on High Throughput Computing or High Performance Computing systems to support their workload. With this move to highly parallel, data or memory intensive systems, the world of astronomy codes and tool-chains must adapt to follow the trend. With more and more codes looking to reach the petascale and exascale regime, utilising powerful compute systems is becoming more important.

We also want to ensure the long-term usability of our codes and this includes making sure it is forward compatible with future systems e.g. by fully utilising available hardware and leveraging the highest efficiency and performance. There are also increasing environmental impacts to consider when it comes to making sure the future of supercomputing is sustainable.

With many different approaches being taken across the community from the use of GPUs and Machine Learning, to novel infrastructure approaches, this session aims to bring code and software developers together from across astronomy. This includes updates and discussions on the future of computing within astronomy from a technical perspective. This could be current code development or porting initiatives, data management or processing pipelines, or sustainability efforts within the computational community. Submissions from active developers and ECRs are particularly encouraged.

61 Dyablo: A New General-Purpose GPU-Accelerated Hydrodynamical Code for Astrophysics

Dyablo is a new high-performance hydrodynamical code designed for large-scale astrophysical simulations, from solar system dynamics to galaxy formation and cosmic reionization. Unlike many existing codes, Dyablo has been designed from scratch to run entirely on the available hardware, whether NVIDIA and AMD GPUs or CPUs accelerated with OpenMP. This architecture enables significant potential speedups compared to traditional CPU-based approaches and even hybrid codes that offload heavy computations to GPUs. Early benchmarking on idealized test cases demonstrates superior performance over RAMSES and strong scaling up to thousands of GPUs or tens of thousands of CPUs, highlighting Dyablo’s potential for next-generation astrophysical modeling. At the conference, we will present the first scientific applications of Dyablo, showcasing its capabilities and future prospects.

62 ExoSim 2: a flexible framework for next-generation simulation of astronomical observations

We present ExoSim 2, a next-generation, fully modular simulator for astronomical observations, initially developed to support the study of transiting exoplanets in the context of the Ariel space mission. Implemented in Python 3 and built on an object-oriented design, ExoSim 2 is publicly available and offers a flexible, open framework for simulating time-resolved spectro-photometric data from space-based, sub-orbital, and ground-based observatories.

Its architecture is based on user-definable Task classes, allowing researchers to customise every stage of the simulation pipeline: from optical and detector models to astrophysical signals and observing strategies. ExoSim 2 also supports temporal effects across multiple timescales, enabling the simulation of a wide range of time-domain phenomena beyond planetary transits, such as stellar activity and instrumental systematics.

ExoSim 2 has been extensively validated against ArielRad and benchmarked across multiple platforms, achieving over 90% test coverage and demonstrating efficient scaling with CPU threads. The simulator is already being applied to other missions, including EXCITE, confirming its versatility and mission-agnostic design.

More than a simulator, ExoSim 2 is a framework for building simulators: a tool that enables researchers to model the physical and observational properties of complex systems. As such, it plays a key role in developing data reduction pipelines, systematics mitigation techniques, and mission planning strategies for the next generation of astronomical instruments.

Speaker: Lorenzo Mugnai (Cardiff University)

63 Astronomical Radiative Transfer and Video Games: a Match Made in the Sun

Radiative transfer is a cornerstone of astrophysics, providing a key tool to model and interpret observations of distant structures, for most of which any form of in situ measurement in impossible. Whilst simplifying approximations are often possible, there are many instances where the observed radiation forms in optically thick plasma outside of local thermodynamic equilibrium (LTE) conditions necessitating detailed and computationally costly treatments of atomic spectral lines where separate regions are connected by a global radiation field.
Astronomy is not the only field that interests itself with the solution of the radiative transfer equation and the propagation of light: the field of computer graphics has long sought efficient approximations to this problem.

In this talk, I will present the DexRT radiative transfer program, a modern and open GPU-accelerated tool for the multidimensional non-LTE radiative transfer problem, and discuss the importance of looking to other fields for enhancements and optimisations. I will also present an overview of our development strategy and plans to minimise maintenance costs.

Speaker: Christopher Osborne (University of Glasgow)

64 Synthesizer: Forward modelling with everything but the kitchen sink

As observational frontiers push into new territory, we must make apples-to-apples comparisons when comparing theory to observation to ensure robust conclusions are drawn. This means transforming models into the observer frame, where we can pinpoint observational biases, explore uncertain parameter spaces, and demystify what “missing physics” really means (if anything). This process requires expensive computations bringing together theory from all corners of astrophysics. For this process to be viable, we must make the most of the hardware at our disposal.

Our newly developed tool, Synthesizer, streamlines this process. This HPC-ready, C-accelerated Python package is built on the principles of usability, efficiency, and flexibility. By simplifying the conversion of simulated and parametric models into observables, Synthesizer empowers researchers to forge robust connections between theory and data. In this talk, I will outline Synthesizer’s capabilities as we approach its v1.0.0 release.

65 Odisseo - Optimized Differentiable Integrator for Stellar Systems Evolution of Orbit

High-performance N-body simulations are crucial for astrophysics, cosmology, and computational physics. Odisseo (https://github.com/vepe99/Odisseo) is a differentiable N-body simulator designed for efficiency, scalability, and long-term usability. Implemented in JAX, it leverages just-in-time (JIT) compilation, automatic differentiation, and GPU/TPU acceleration
to provide fast, vectorized, and distributed pairwise force calculations. Odisseo supports external potentials and enables gradient-based optimization, making it a powerful tool for scientific inference and machine learning applications. Its JAX-based architecture ensures modularity, ease of extension, and long-term maintainability, fostering community-driven development.

66 jf1uids - differentiable (magneto)hydrodynamics for astrophysics in JAX

We present jf1uids (https://github.com/leo1200/jf1uids), a differentiable magnetohydrodynamics (MHD) simulator written in JAX, scaling to multiple GPUs. Our open source code features a modern inherently divergence free approach to MHD, (near-)energy-conserving self-gravity stable at discontinuities, a conservative geometric formulation for radially symmetric simulations and multiple physics modules in development, starting with cosmic rays and stellar winds. It's differentiability and scalability make jf1uids a unique tool for bringing together classical astrophysical simulations and machine learning. Being written in high-level Python / JAX, jf1uids allows for rapid development and contributions from a broad community.

67 Optimizing Response Time in Robotic Telescope Scheduling Using Deep Reinforcement Learning

The New Robotic Telescope (NRT) represents a significant advancement in autonomous astronomical observation, with core science goals requiring response times under 30 seconds for transient events. Traditional scheduling approaches often rely on fixed priority rankings that inadequately address time-sensitive observations, especially as astronomical surveys like LSST generate unprecedented volumes of alerts requiring rapid follow-up.
We present a novel scheduling framework that employs Deep Q-network reinforcement learning to optimize the critical trade-off between observation priority and response time. Our research demonstrates that conventional priority-based scheduling can be significantly enhanced by incorporating a response time parameter within the reward function. Through comparative analysis of different reward weight configurations, we identified a non-linear relationship where a 1:2 priority-to-response-time weighting achieves optimal performance - maintaining traditional priority distribution while dramatically improving response time success rates from ~12% to ~82%.
This research addresses the computational challenges of modern time-domain astronomy by developing an adaptive, learning-based scheduler that can process large alert streams efficiently. Our implementation demonstrates how machine learning techniques can be leveraged to maximize scientific return in resource-constrained environments, particularly when competing objectives must be balanced. The scalable approach makes it suitable for next-generation observational facilities producing massive data volumes requiring real-time decision-making.

68 ExaGRyPE: Numerical Relativity Solvers Based upon the Hyperbolic PDEs Solver Engine ExaHyPE

ExaGRyPE is a suite of solvers for numerical relativity based on ExaHyPE 2, our second-generation Exascale Hyperbolic PDE Engine. This solver tackles the Einstein equations/relativistic hydrodynamics equations under a 3+1 foliation, with a focus on compact object spacetimes. The implementation utilizes a block-structured Cartesian grid with higher-order Finite Difference schemes and adaptive mesh refinement while enabling massive parallelism through message passing, domain decomposition, and task parallelism.
Our approach formalizes simulation creation as a sequence of lowering operations, where abstract logical tasks are broken down into progressively finer tasks until reaching a C++ executable level. The program logic is specified through a domain-specific Python interface, which maps to numerical tasks, then to technical tasks for parallelization, and finally to task graphs containing PDE evaluations, initial conditions, and boundary conditions. This architecture creates a rigorous separation of concerns, shielding users from technical details and simplifying the development of novel physical models. This approach enables researchers to efficiently develop and deploy novel physical models while leveraging the full computational potential of exascale systems.
In this talk, we are going to present the ExaGRyPE architecture and demonstrate its capabilities through comprehensive benchmarks. We will also highlight our unique solver-coupling feature, which allows us to seamlessly integrate finite volume scheme for relativistic hydrodynamics within our high-order finite-difference framework for spacetime evolution.

Speaker: Han Zhang (durham university)

15:35 Flash Poster Presentations

Advancing Our Understanding of the Solar Corona-Wind Connection in the Age of Solar Orbiter and Parker Solar Probe

Organiser: Jesse Coburn; co organisers: Deborah Baker, Luca Franci, Alexander James, Pauline Simon, Stephanie Yardley

The Solar Orbiter and Parker Solar Probe missions have both been operating for several years now providing state-of-the-art in situ measurements of the solar wind and remote sensing observations of its source regions on the Sun. They have ventured closer to the Sun than ever before providing new insights into the mechanisms that heat the corona and accelerate the solar wind. This unprecedented view of the solar corona-wind connection with the aid of advanced magnetic field modelling permits precise identification of the solar wind source regions (such as coronal holes and active region boundaries). In particular, we are able to put observational constraints on theories that invoke magnetic field reconnection and energisation by plasma turbulence and waves to explain coronal heating and solar wind acceleration. In this session, we will celebrate and discuss the latest advances in solar wind and solar corona research. We encourage observations from Solar Orbiter, Parker Solar Probe, Daniel K. Inouye Solar Telescope (DKIST), Advanced Composition Explorer, Swedish 1-m Solar Telescope, Solar Dynamics Observatory, Hinode and other Heliospheric observatories.

69 MHD wave heating in the complex solar atmosphere

Since the middle of the last century, it has been known that the atmosphere of the Sun is orders of magnitudes hotter than its surface. Over the years, many studies have looked at the potential role of MHD waves in sustaining these high temperatures. Using 3D MHD simulations of transverse, Alfvenic waves, we look at the role of the complexity of the magnetic field and the power spectrum of the wave driver. We focus on the efficiency of the wave-based heating in our models, in particular whether heating provided by the waves can balance coronal losses. Using wave identifiers based on fundamental wave characteristics such as compressibility and direction of propagation we show that, for particular line(s)-of-sight and assumptions about the magnetic field, we can correctly identify properties of the Alfvén mode in synthetic observations of a transversely oscillating loop.

Speaker: Ineke De Moortel (University of St Andrews)

70 Total Power and Low-energy Cut-off Time Evolution of Solar Flare Accelerated Electrons Using X-Ray Observations and Warm-Target Model

A primary characteristic of solar flares is the efficient acceleration
of electrons to nonthermal deka-keV energies. While hard X-Ray (HXR)
observation of bremsstrahlung emission serves as the key diagnostic of
these electrons. In this study, we investigate the time evolution of
flare-accelerated electrons using the warm-target model. This model,
unlike the commonly used cold-target model, robustly determines the
low-energy cut-off in the nonthermal electron distribution, so that the
energetics of nonthermal electrons can be deduced accurately. Here, we
examine the time-evolution of nonthermal electrons in flares
well-observed by the RHESSI and the Solar Orbiter (SolO, using the STIX
instrument) spacecrafts. Using spectroscopic and imaging HXR
observations, the time evolution of the low-energy cut-off of the
accelerated electron distribution, the total power of nonthermal
electrons, total rate of nonthermal electrons, and excess thermal
emission measure from the nonthermal electrons, are investigated. We
find that the time profile of the low-energy cut-off of the accelerated
electron distribution shows a high-low-high trend around the HXR bursts
of flares, while the time evolution of the total rate of injected
electrons shows a low-high-low behavior. Although the total power of
nonthermal electrons is sensitive to the cut-off energy, the temporal
variation of the flare power follows the temporal variation of the
acceleration rate. We further find that the highest contribution of the
excess thermal emission measure coming from thermalization of injected
electrons takes place around the hard X-ray peak.

71 An outflow equilibrium model for the solar corona

Many space weather forecasting and scientific applications would benefit from improved extrapolation of the solar coronal magnetic field, since this acts as the main “boundary condition” for models of the heliospheric magnetic field and solar wind. I will present a practical extension to the PFSS (potential field source surface) model to incorporate an axisymmetric solar wind. A steady state is obtained by balancing magnetic relaxation against the opening effect of the solar wind outflow. Perhaps surprisingly, but thanks to the axisymmetric flow, the problem is susceptible to an efficient eigenfunction/spectral treatment similar to that used in our PFSS solver (“pfsspy”), so remains practical for “real-time” forecasting. Preliminary exploration shows that the model removes the artificial source surface, leading to more realistic coronal streamer morphologies. It also enhances the open flux in a time-dependent way, partially addressing the well-known “open flux problem”.

Speaker: Anthony Yeates (Durham University)

72 Magnetohydrodynamic Wave Modelling in the Solar Atmosphere and their Observational Consequences

Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere and are key in many models for seismological or energy conversion processes. Coronagraphs such as Metis on board Solar Orbiter have already detected wave-like disturbances and other such instruments on board Aditya-L1 and PROBA-3 are likely to follow observing them at unprecedented spatial and temporal resolutions, opening pathways to study MHD waves in the outer corona. Such white light images are crucial to understand wave properties which are manifested as density variations, as the wave motions and the background solar wind displace the local plasma. Using 2.5-D MHD modelling, we study these waves in the solar atmosphere as they evolve along open and closed magnetic field structures such as coronal holes and helmet streamers as far as up to ~20 solar radii, also carried by a background solar wind that transitions from being sub-Alfvénic to super-Alfvénic. Our model takes into account spherical expansion, gravitational stratification, thermal conduction, and radiative cooling, and provides indications on the detectability of such waves, observed as density variations by Metis and the new-generation coronagraphs from different vantage points.

Speaker: Anmol Kumar (University of St Andrews)

73 Connection between fundamental processes and large-scale heliospheric structure from Parker Solar Probe’s prime mission

Parker Solar Probe was launched nearly 7 years ago and within a few months became the first spacecraft to study the inner heliosphere twice as close to the Sun than ever before. Each year, PSP’s perihelion has been moving closer to the Sun, last year reaching a distance of less than 10 solar radii, nearly 7 times closer than any other spacecraft. An important milestone was reached in 2021 when PSP crossed the Alfven surface allowing the sub-Alfvenic flow to be measured for the first time, and revealing how this evolves into the super-Alfvenic solar wind. In this talk, a selection of results from PSP will be reviewed, focussing on the broader picture of what we have learnt given that we are now nearing the end of the prime mission. Particular themes will involve the nature of fundamental plasma processes in the near-Sun environment, the connection between those processes and the structure/sources of the solar wind, the role they play in shaping and interacting with the large-scale properties, understanding the evolution from the sub-Alfvenic flow into the heliosphere, and progress towards key mission goals, such as understanding solar wind heating and acceleration. New questions that have arisen will also be highlighted, along with future work that will be needed to answer them.

74 Switchback generation from the evolution of Torsional Alfvén waves

Switchbacks are large Alfvénic deflections , or even reversals, of the magnetic field in the solar wind. Many authors have suggested that switchbacks are linked to processes low in the solar atmosphere such as interchange reconnection, but the manner of this connection remains unclear. Torsional Alfvén waves are known to be naturally produced by impulsive interchange reconnection events such as coronal jets and jetlets, as well as chromospheric swirling motions. Here we present a new study of how such Torsional Alfvén waves can evolve into switchbacks in a super-radially expanding solar wind. We find that the waves evolve into a vortex ring configuration (similar to hydrodynamic smoke and bubble rings) involving Alfvénic radial field reversals. We show that the maximum deflection associated with this evolution is relatively insensitive to the injection time or driving speed, provided a sufficient amount of twist is injected in total. Overall, our findings support the idea that Torsional Alfvén waves launched into the solar corona by interchange reconnection or surface swirling motions can provide seed perturbations for the formation of switchback radial field reversals within the solar wind.

75 Investigating the dynamic sources of fast solar wind from low-latitude coronal holes

Low-latitude coronal holes can produce fast solar wind characterized by rapid fluctuations rather than a steady flow. Despite significant advances in solar physics, the precise mechanisms behind the formation of this fast solar wind remain elusive. In this study, we analyze multiple sources of such wind. By linking in-situ measurements from the Solar Orbiter's instruments to their potential source regions through ballistic backmapping and potential-field source-surface modeling, we gain new insights. Coronal spectroscopic data from Hinode’s Extreme Ultraviolet Imaging Spectrometer reveal a complex interplay of upflow and downflow regions within these coronal holes, highlighting their intricate nature. These regions exhibit a mix of open and multi-scale closed magnetic fields, whose interchange reconnections are consistent with the observed up- and downflows, as well as the strahl directions and freeze-in temperatures found in in-situ data. Additionally, the SPICE spectrometer on board Solar Orbiter allows us to study other layers of the solar corona. We emphasize the role of magnetic reconnection in generating the observed upflows, downflows, and intermediate wind streams. The interaction between open and closed magnetic fields in coronal holes and active regions is crucial in this process. Observing the behavior of sulfur with SPICE may provide clues to pinpoint where interchange reconnection is occurring.

76 Probing Solar Turbulence Through Angular Broadening of Radio Sources with MeerKAT

The study of solar turbulence and density fluctuations is essential for understanding the physical processes governing the heliosphere, particularly the behavior of the solar wind and its role in space weather. These turbulent structures can significantly influence the observed properties—such as angular size and position—of compact extra-solar radio sources. In this work, we utilize the dynamic spectroscopic imaging capabilities of the MeerKAT array in the L band to observe multiple compact radio sources located as close as 2 degrees from the solar disk. With 64 antennas, MeerKAT offers high signal-to-noise imaging performance, enabling the detection and analysis of faint radio sources despite the presence of strong solar emission. By examining source characteristics across a range of solar elongations and frequencies, we find that the observed angular broadening is consistent with theoretical predictions of scattering by solar wind turbulence. Furthermore, measured elongation directions and axial ratios provide insights into the magnetic properties and the anisotropic nature of the turbulence. This study demonstrates the potential of interferometric radio observations in probing heliospheric turbulence and contributes to a more comprehensive understanding of its impact on radio wave propagation.

The Role of Star Clusters in Star Formation from Local to Galaxy Scales

Organisers: Anne Buckner; co organisers: Ahmad Ali, Sean Linden, Hektor Monteiro, Steven Rieder, Christina Schoettler, Nick Wright

Star clusters are thought to be fundamental building blocks of our galaxy as most stars form in clustered environments of some sort. As such they provide crucial insights into the physics underpinning star formation from the local ISM to galaxy scales. For example, individual clusters are ideal laboratories to study stellar evolution and the mechanics of N-body stellar systems; while cluster populations can be used to trace galactic structure and investigate the physical processes of galactic evolution.

Unfortunately, the mechanisms of cluster formation, effect local and galactic environmental conditions have on this, as well as clusters longer term evolution,remain unclear. To better constrain them requires a multi-pronged analysis of (1) the internal structure and dynamics of the stellar and gas components of individual clusters; (2) cluster populations, comparing variation in their properties (age, mass, stellar composition) as a function of galactic environment and conditions.

This session will bring together a wide range of observers and modelers in the field of star clusters, from small-scale studies of individual clusters through to galaxy-scale population studies, to build up a cohesive picture of our current understanding of the critical role clusters play in star formation and the evolution of galaxies. We will focus the discussion around (1) new findings obtained using state-of-the art observations (e.g., Gaia & JWST) and simulations; (2) the best techniques/tools to effectively analyse and compare results from these.

14:15 Welcome remarks

77 What fraction of star formation occurs in clusters...and why do we care?

In this review I will address the question of what fraction of star formation occurs in 'clusters'. I will first discuss the various definitions of clustered star formation, before focusing on the important question of why this matters for other research disciplines in astrophysics. As a spoiler, I can reveal now that I won't (can't) answer the first part of the question in my talk title.

78 The Imprint of Clustered Star Formation on the Kinematics of Young Stars in the Solar Neighbourhood

Recent surveys have provided a much more complete census of nearby star-forming regions and their populations of young stars. Notably, the Gaia mission has revealed the 3D structures of these regions and the kinematics of their members. On spatial scales ranging from molecular cloud clumps to giant multi-kpc filaments, the processes of molecular cloud assembly, turbulent collapse, and dispersal initialise the dynamical states of young stellar clusters and associations. On small scales, velocity dispersions in clouds are reflected in the velocity dispersions of the young stars they form (e.g., the Trifid Nebula), and the turbulent motions in clouds are reflected in the subclustering of young stars in position-velocity space (e.g., the North America/Pelican Nebulae). On intermediate scales, the disruption of molecular clouds by stellar radiation and winds likely drives the expansion and dispersal of young clusters and associations in many star-forming regions due to both the disruptive effects of mass loss and star formation in expanding cloud shells (e.g., the Cygnus X region). Finally, on multi-kpc scales, the assembly of molecular gas into giant filaments imprints itself on the Galactic orbits of young clusters and associations. Together, these multi-scale processes help explain why most massive star-forming regions do not produce bound open clusters and why stellar associations exhibit complex internal kinematics.

79 What Time Can Tell Us About Space: A Study of Variability in Young Stellar Objects

Time-resolved data is a powerful tool to investigate spatial scales well beyond the range of direct imaging and ‘using time to map space’ is the only feasible method to study small-scale processes and structures, for a statistically significant numbers of sources. I will present my study of time variability, in the spectroscopy and photometry, of young intermediate-mass stars comprising of HAeBe and massive T Tauri stars. I will also
highlight our analysis from the North-PHASE legacy survey on the young stellar cluster, NGC 2264.

We studied the variability of 26 well-known young objects, with analysis data received by CARMENES and supplemented by archive data. We found that variability must be determined, as stellar properties change significantly depending on how they have been measured in the photometry. The time-resolved spectra assisted in distinguishing rotational modulation from accretion variations, as we measured the variability in velocity and relative intensity for different lines (including metallic ones). This work also unveils the structures and processes in these objects at the relevant scales for inner planet formation.

North-PHASE investigates stellar variability on timescales from days to years for thousands of young stars. With Gaia, we studied the star formation history of NGC 2264 and explored its subcluster structure. We used variability indices to detect different types of variable stars in NGC 2264, which unveiled members that are YSO proper motion outliers. Thus, we can complete the results of Gaia, exposing a diverse variable star population and revealing the true kinematics of the entire cluster.

80 A Multi cadence Study Of The Variable Stars In Tr 37: Accretion Stability, Inner Disk Properties And Activity

North PHASE survey is a 5 year survey that will be using time-resolved, large field data, to unveil structures and processes in young stars (YSO) at the relevant scales for inner planet formation, while also studying the connection between stars, their formation history, and their clusters, independently of astrometry.

Studying young star cluster Trumpler 37 (Tr37) provides key insights into star formation, protoplanetary disk evolution, and stellar feedback mechanisms from local to galactic scales. Tr37, a 4 Myr old cluster contains a diverse population, including massive OB stars and low-mass T Tauri stars. This makes it an ideal laboratory for examining early stellar evolution and the role of cluster environments in shaping star formation outcomes.
Tr37 hosts numerous stars with circumstellar disks, including classical T Tauri stars and transition disk objects, allowing the study planet-forming processes and disk dissipation mechanisms. The presence of massive stars in Tr37 significantly influences its surroundings through intense UV radiation and stellar winds, leading to photoevaporation of disks and triggered star formation in nearby gas clouds.
Additionally, Tr37 exhibits sub-clustering, providing a natural setting to investigate cluster dynamics and eventual dispersion into the galactic field population. Observing Tr37 helps bridge the gap between local star formation studies and large-scale galactic evolution, offering a framework for understanding star formation in distant starburst regions and galaxies. By analyzing clusters like Tr37, astronomers can better constrain the timescales and physical processes governing stellar birth, disk evolution, and the long-term impact of stellar feedback on the interstellar medium.

81 Statistical Theory of Three-Body Interactions in Clusters

Three-body interactions play a dominant role in the evolution of dense stellar systems, such as clusters, and in particular in the dynamical formation of gravitational-wave sources. Indeed, one of the channels for binary formation during cluster core collapse is via the "collision" of three initially-unbound objects. In this talk I will describe an analytical formalism to calculate the properties of such three-body binaries, including their non-thermal eccentricity distribution and their formation rate, based on a probabilistic analysis of unbound three-body encounters, and discuss some implications for the population of eccentric, wide binaries observed by Gaia. This approach can model general binary-single encounters between hard binaries and single stars, and I will describe how to do so. Hard binaries go on to harden via subsequent three-body encounters, and I will also model the evolution of their properties under such interactions, which gives rise to a unique eccentricity distribution.

Speaker: Barry Ginat (University of Oxford)

82 The Long-Term Evolution and Dissolution of Young Stellar Clusters

Stars will typically spend the first few million years of their lives in their natal star-forming regions. The initial densities in these regions often mean young stars are much more likely to experience the effects of close encounters, massive star stellar winds and potentially even nearby supernovae. Therefore, understanding the dynamical evolution of star-forming regions is key to understanding star (and planet) formation and it tells us much about the stars' early lives. However, the dissolution of star-forming regions into the Galactic disc is much less well understood. Does the dissolution rate depend more on the initial mass, density or virial state of the star-forming region? Using N-body simulations of the first 100Myr of a star-forming region, we aim to understand the effects of various factors on star cluster dissolution. In particular, we focus on the effects of an external tidal field on star-forming regions of varying radii, mass, density and initial degree of spatial and kinematic substructure. In this talk I will present the results from a suite of simulations, and discuss the implications of these regions' evolution on star formation, and the young planetary systems that form simultaneously with the stars.

The Golden Era of Gravitational Lensing: from Micro to Macro

Organiser: Maximilian von Wietersheim-Kramsta; co organisers: Aristeidis Amvrosiadis, Djuna Lize Croon, Leo Fung, Harshnoor Kaur, David Lagattuta, Samuel Lange, Gavin Leroy, Richard Massey, Nency Patel, Kai Wang

From the distortions of the images of stars due to exoplanets to the coherent warping of the relic radiation from the Big Bang, gravitational lensing (GL) is a phenomenon ingrained in the laws of gravity allowing us to probe astrophysics over a wide range of scales. Upcoming surveys, such as Euclid, Rubin LSST, SKA and Roman, will for the first time map weak GL over the whole sky from billions of sources. Simultaneously, instruments such as JWST, ALMA, ELT and HWO will observe strong GL with unprecedented resolution, while LIGO/VIRGO, LISA and IPTA can measure the impact of GL on gravitational waves. Truly, we are on the cusp of probing gravity, the nature of dark matter and the evolution of the Universe over untested regimes with unparalleled precision.

To mark this golden era in the field, we will bring together expert GL modelers, theorists, and observers to showcase and discuss their research. The session will focus on the scientific impact of GL probes: how they will inform novel theories, prepare the next generation of simulations, and improve data analysis techniques, while addressing current tensions. Through contributed talks, we will hear about a wide range of GL subfields with the aim of fostering collaboration and awareness within the field.

14:15 Welcome remarks

83 The roadmap to 100,000 strong lenses with Euclid

A decade ago, it was forecasted that the Euclid space telescope would discover ~150,000 strong gravitational lenses, revolutionising the field. However, it was previously unknown if it would be possible to extract these from the total 1.5 billion galaxies that Euclid will observe. In the recent early data release (Q1), which represents the first 0.45% of the full Euclid survey, we discovered 500 strong lenses through the combined power of machine learning and citizen science. Notably, this sample includes exotic lenses, such as 4 new double-source-plane lenses and ~30 edge-on disc lenses, despite the machine learning networks not being trained to find such objects. I will present these new lens discoveries, how the properties of these lenses compare to forecasts, and the lessons learnt about how to find strong lenses in large surveys. This sample provides the first glimpse into what is achievable by Euclid, and I will discuss our strategy to scale this up to DR1 and the full Euclid survey, where we are on track to discover ~10,000 and ~100,000 strong lenses respectively.

84 Constraining Dark Substructures Beyond the Diffraction Limit with Cluster Lens

Properties of dark matter (DM) substructures deliver important insight about the interaction among the DM constituents. Detection of DM substructures were made possible in the last decade with a parametric method known as ‘gravitational imaging’, yielding successful detections of sub-haloes of mass $M_{sub} > 10^8$ $M_\odot$. For substructures smaller than $10^8 M_\odot$, the detection is significantly challenged due to the lack of spatial resolution and simultaneously the degeneracies in the parameter space.
In this talk, I explore the rationale for detecting dark substructures from gravitational lensing. In particular, how tiny dark substructures with characteristic scales below the diffraction limit by most optical telescopes can be detected. I will demonstrate that a conservation theorem in classical optics - namely the Optical Liouville Theorem, can be exploited to constrain tiny substructures beyond the diffraction limit. Solely based on a generic theorem in optics, the method is fully model-independent, and parametric modeling of the lens system is not required. The achievable precision of the method is evaluated with lensing simulations, and is applied on the JWST cluster SMACS 0723. I will conclude the talk with some ongoing works that extend from the method introduced.

85 Empirical dark matter halo profiles

Dark matter halos, central to much of cosmology and astrophysics, are often summarised by their radial density profiles. These are typically assumed to have a fixed functional form (such as NFW) inspired by simulations, with a number of free parameters that can be constrained by fits to observational data. However, the approach of relying on simulations is undesirable, as the dark matter density profile depends on the adopted dark matter model (e.g. cold vs. self-interacting dark matter) and the baryonic physics implementation, both of which are highly uncertain.
To address this, we have developed a new method to constrain the functional form of halo density profiles directly from weak lensing data, without input from simulations. This is done using a novel symbolic regression algorithm called Exhaustive Symbolic Regression (ESR), which learns the optimal analytic expression to fit a set of data whilst using minimum description length, a tool from information theory, to penalise unnecessary complexity. Hence our algorithm can identify the halo profile with maximum empirical accuracy.
We apply ESR to weak lensing measurements from the Hyper Suprime-Cam (HSC) survey for X-ray-selected galaxy groups and clusters from the XMM-XXL survey. Our method identifies dark matter density profiles that provide a better fit than the standard NFW profile. With the influx of high-quality data from upcoming surveys, our method will improve inferences that rely on assumed density profiles and provide strong empirical constraints on the nature of dark matter.

86 The era of simulation-based inference for gravitational lensing

I will review the recent significant advances in statistical learning that have led to gravitational lensing analyses using "simulation-based inference" (SBI). These new statistical approaches permit data analyses that would otherwise be impossible. I will review results from the Kilo-Degree Survey and the Dark Energy Surveys, both using SBI for classical 2pt statistics and also beyond 2pt statistics (including AI-powered map-level results) – these have led to the tightest constraints (to-date) on dark energy from weak lensing data. I will cover the opportunities and challenges for these methods for Rubin LSST & Euclid.

[e.g. https://arxiv.org/abs/2212.04521, https://arxiv.org/abs/2404.15402, https://arxiv.org/abs/2403.02314 ]

87 High resolution dark matter cartography with JWST: Overdensity properties studied through their weak lensing signal

Weak gravitational lensing by large-scale structures offers a powerful technique for directly mapping the distribution of matter in the Universe. Following this principle, we recently produce the highest-resolution dark matter maps of the 0.54 square degree COSMOS-Web field to date. These maps are derived from weak lensing cosmic shear measurements using the James Webb Space Telescope (JWST) NIRCam, for which our weak lensing source catalogues achieves a density of approximately 150 galaxies per square arcminute.
In this talk, we would like to detail the state of the art methods assembled for the first time to produce these maps and its astrophysical impacts. We would discuss key aspects of weak lensing theory, the enhanced Kaiser-Squires mass inversion (KS+) method and the MRLens filtering approach used to generate the maps while mitigating systematic effects. Then, we apply a fast multiscale algorithm to detect the galaxy clusters of the field based on their weak lensing signal and compare their properties with X-ray and optical clusters. We compare the JWST-derived maps with those from the Hubble Space Telescope (HST) and highlight the locations of new galaxy clusters detected based on their weak lensing signal.

15:35 Poster Flash Presentations

Active Galactic Nuclei – from ISCO to CGM and from cosmic dawn to the present day

Organisers: Carolina Andonie, Vicky Fawcett, Jiachen Jiang, Amy Knight, Amy Rankine, Matthew Temple

AGN are multi-scale phenomena, with interesting physics operating from the event horizon to the circumgalactic medium. In this session, we will bring together research on different aspects of SMBH accretion physics, AGN population studies, and AGN demographics. In this session we will cover:

Accretion discs, jets and outflows in the centers of AGNs. With the recent launch of Xrism and the ongoing success of existing missions, there is a wealth of data from high-energy telescopes. We will accept presentations of observational data analysis, observation-related numerical simulations, and theoretical research for this first session. We also encourage presentations of multi-wavelength and multi-messenger observations.

Obscuration in AGNs from both dust and gas, examining the accretion and host galaxy properties of different AGN populations such as obscured AGNs, red quasars, and HotDOGs. What can these different AGN populations tell us about the SMBH-galaxy connection?

Current and future large-scale surveys such as SDSS, 4MOST, MOONS, WEAVE, DESI, LSST, Euclid and LOFAR. These facilities will produce unprecedented samples of millions of AGN. With the UK taking a leading role in many of these projects, NAM is an excellent opportunity to examine the completeness of our AGN census, and the accretion, galactic and large-scale environmental properties of AGN across luminosity, stellar masses, and cosmic time.

14:15 Welcome

Adam Ingram
Amy Knight
Amy Rankine
Andrew Young
Carolina Andonie
Jiachen Jiang
Matthew Temple
Vicky Fawcett

88 The Broadband View of the Bare Seyfert PG1426+015: Relativistic Reflection, the Soft Excess and the Importance of Oxygen

A long-standing issue in X-ray studies of AGN is the nature of the "soft excess", an excess of flux seen below ~2keV when the standard AGN continuum that reproduces high-energy X-ray emission is extrapolated down in energy. One of the leading interpretations is that this feature is related to relativistic reflection from the accretion disc, resulting from a combination of relativistically broadened emission lines and the free-free continuum present in reflection models at low energies. To explore this further we present results from a deep, coordinated XMM+NuSTAR observation of the 'bare' type 1 Seyfert PG1426+015, a source of particular interest as the most massive reverberation-mapped black hole to date (log[M/Msun] = 9.0). The broadband spectrum unambiguously reveals the presence of relativistic reflection (broad iron emission, Compton reflection hump) as well as confirming the presence of the strong soft excess reported previously. We test whether relativistic reflection can successfully account for the soft excess along with the higher-energy reflection features, utilizing the two most-commonly used reflection codes (REFLIONX, XILLVER). Ultimately we find that both models are able to successfully reproduce the soft excess, though in the case of the XILLVER model this is contingent on reducing the strength of the OVIII line included in the model, as otherwise this feature prevents the model from reproducing the data. Though we focus on PG1426+015 as a test case, this OVIII issue likely has broader implications for recent attempts to explore the reflection model for the soft excess in AGN more generally.

89 Constraining black hole spin in PG 1535+547 amidst complex multi-layered absorption

We present a spectroscopic analysis of XMM-Newton and NuSTAR observations of the 'complex' NLS1 PG 1535+547 at redshift $z=0.038$. These observations span three epochs: 2002 and 2006 with XMM-Newton alone, and a coordinated XMM-Newton and NuSTAR observation in 2016, covering the $0.3-70$ keV energy range. The X-ray spectra across all epochs exhibit both neutral and ionized absorption, along with reflection features from the accretion disc, including a prominent Compton hump in the broadband data. Notably, the spectral shape varies across epochs. Our analysis suggests this variability being attributed to changes in both line-of-sight absorption and intrinsic emission. The source is obscured by multiple layers of partially and/or fully covering neutral and ionized absorbers, with neutral column densities ranging from undetectable levels in the least obscured phase to $\sim3-5\times10^{23} ~ \rm cm^{-2} $ in the most obscured phase. A clear warm absorber is revealed during the least obscured phase. The continuum remains fairly consistent ($\Gamma \approx 2.2\pm0.1$) during the first two observations, followed by a substantial flux decrease (by a factor of $\sim7$ in the $2-10$ keV band) in 2016 compared to 2006. The 2016 data indicates the source is in a reflection-dominated state during this epoch, with a reflection fraction of $R > 7$ and an X-ray source located at a height $\leq 1.72 ~ R_g$. Simultaneous fitting of the multi-epoch data suggests a rapidly rotating black hole with a spin parameter, $a > 0.9$. These findings imply that strong light-bending effects may account for the observed continuum flux reduction.

90 Beyond Reverberation: The Complex Nature of AGN Variability Revealed in Fairall 9

Standard accretion disc theory predicts that AGN accretion disc cannot vary on observable time-scales, instead attributing the observed optical/UV variations to the re-processing of X-rays originating from a low-density corona. In recent years the intensive black hole monitoring campaigns (IBRM) have challenged this picture, often showing poor correlations between the optical/UV and X-ray as well as optical/UV variability amplitudes inconsistent with that expected from disc reprocessing. Fairall 9, a local bare Seyfert 1 AGN, was recently subject to a ~1000 day IBRM campaign, providing one of the richest current IBRM datasets and a unique window into its accretion structure. These data show a sharp rise after ~300 days in the optical/UV, with a corresponding evolution in the spectral energy distribution (SED) suggesting a global change to the system driven by an increase in the mass-accretion rate. Here I will show results indicating a significant departure from standard accretion disc theory, and suggest that even non-changing-look AGN are possibly non-stationary on observable time-scales, impacting how we interpret future monitoring campaigns.

91 Measurements of the X-ray Luminosity Function of AGN at $z=4-10$

AGN play an important role within their host galaxies, influencing their evolution and growth. Little is known about the initial formation and evolution of AGN in the early Universe. However, new observations by JWST are unveiling larger populations of these sources than previously expected, indicating lower luminosity AGN may be more common in the $z>6$ Universe, when significant galaxy build up is occurring. To obtain robust and extensive constraints on this early AGN population we need measurements of the AGN X-ray Luminosity Function (XLF), particularly for the intermediate luminosities that dominate blackhole mass assembly at $z>6$.

I will present new measurements of the high-redshift XLF using Chandra-selected AGN within the COSMOS2020 galaxy survey. We identified counterparts to X-ray sources and pushed the limit of Chandra’s sensitivity to identify sources below the normal sensitivity and obtain X-ray constraints in the very high redshift regime. We are thus able to place constraints on the space density of moderate-luminosity AGN out to $z\sim10$. Our measurements reveal higher space-densities than expected, based on the extrapolation of XLF models from lower redshifts. Furthermore, we find evidence that a large fraction of the early AGN population are heavily obscured; correcting for this obscuration further increases our measured space densities at moderate X-ray luminosities. Our constraints begin to bridge the gap between the bright-end of the QLF and the latest JWST observations of very early, low-luminosity AGN, indicating that a larger fraction of the first galaxies likely play host to a rapidly growing SMBH than previously thought.

92 The wind properties of the X-ray selected SDSS-V quasar sample

Quasar winds are evident in rest-frame UV spectra in the form of blueshifted broad emission lines. How such winds are launched – and how such launching relates to the physical state of the accretion disc system that powers quasars – remains a key open question. SDSS-V follow-up of eROSITA sources is yielding a large quasar sample for which we have access to their wind properties and (via measurements of the X-ray, UV and optical emission) constraints on their accretion state. I will present new measurements for a sample 4000 quasars at redshifts 1.5-3.5 that quantify how the strength of quasar accretion disc-winds (from the CIV emission line) depends on both the strength of the UV ionising continuum (probed via HeII emission) and the X-ray properties derived from the eROSITA spectra (i.e., photon index and column density). We show that quasars with a given X-ray luminosity have a broad range of wind properties that appear to depend most strongly on the strength of the UV-bright inner accretion disc (revealed by the HeII emission line). A strong UV component can lead to over-ionisation of the wind such that the outflow strength is decreased. These results point to radiation-driven winds whose strength and presence are highly sensitive to the physical structure of the accretion system. The X-ray photon index and column density, however, do not appear to impact the strength of the wind. With this information in hand we can gain a new perspective of the wind properties of the X-ray selected quasars.

93 Flipping the switch: what can we learn from the MIR emission of changing-look AGN?

Changing-look active galactic nuclei (CLAGN) are objects that show striking increases or decreases in optical AGN broad line emission over time; e.g., Ricci & Trakhtenbrot, 2023. These events are thought to be mostly the result of dramatic changes in accretion state, and as such provide a laboratory for studying the variation in accretion processes that is known to exist in AGN, but not usually observable on useful timescales or in such grand fashion. The influence of this can be observed across the EM spectrum, from X-rays (e.g., Liu et al., 2022) to mid-infrared (MIR; e.g., Sheng et al., 2017). CLAGN are being discovered in rapidly increasing numbers, due in part to the rise of large spectroscopic surveys like the Dark Energy Spectroscopic Instrument (DESI) - combining this with older SDSS spectroscopy has produced the largest sample of CLAGN to date: ~550 largely previous unknown CLAGN (Guo et al., 2024). With this extensive sample we can show that on a population scale CLAGN are inherently different to comparable non-changing look AGN. In this talk I will demonstrate how we can use longer-term MIR light curves in concert with the two discrete optical spectra to investigate how CLAGN evolve over time. I will discuss how these results can help understand the changes in accretion processes, show that apparent CLAGN can include other accretion events (such as TDEs; e.g., Clark et al., 2025), and that true CLAGN alone are a diverse class of objects.

Speaker: Claire Greenwell (Durham University)

CGreenwell_ test presentation.pptx

94 Dust in the Wind: extended dust in the circumnuclear regions of AGN as tracers of feedback

A surprising result from mid-infrared (MIR) interferometry of nearby active galactic nuclei (AGN) is that a major fraction of the parsec-scale dust emission is elongated in the polar direction perpendicular to the accretion plane. This has spurred a new paradigm for the nuclear structure, where a dusty conical wind carries a substantial outflow of material into the interstellar medium. I will present JWST-centric multi-wavelength studies of nearby AGN with the aim of identifying and understanding polar emission and its relationship to gaseous outflows. I will outline the modern methods we employ to overcome the complex nature of our datasets and the first characterisation of resolved dust continuum emission on 100 pc scales in a local Seyfert galaxies. With JWST, we are able to measure the size and shape of the polar dust, explore its composition, and directly trace its interaction with neighbouring gas, zooming in on the sites of feedback in action.

15:30 Poster Talks #1

15:45 Coffee Break and Cakes for Good (charity cake-bake sale)

Cakes for Good is a monthly charity bake sale held in the Durham Astronomy department, which we are inviting NAM attendees to join. So come along to try some delicious cakes, with donations going to the Great North Air Ambulance Service.

15:45 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

16:15 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

Magnetohydrodynamic waves in the solar atmosphere: new insights from advanced observations and modelling

Organisers: Tim Duckenfield, Shahin Jafarzadeh, Samuel Skirvin

Building on the UK’s legacy of groundbreaking MHD wave research, this session explores the crucial role of magnetohydrodynamic (MHD) waves in solar atmospheric dynamics and energy transport. MHD waves are powerful tools for probing plasma conditions and are thought to be key to heating the corona and driving the solar wind. This is a critical moment for MHD wave research, with new high-resolution observations from facilities like DKIST (with strong UK involvement) and SUNRISE providing unprecedented detail of magnetic oscillations across the solar atmosphere. These observations, combined with advanced modelling techniques, are revolutionising our understanding of wave generation, propagation, and dissipation across different atmospheric layers (i.e., photosphere, chromosphere, transition region, and corona) through multi-line observations and sophisticated numerical models. This session aims to connect researchers within the broad field of MHD wave research to discuss recent breakthroughs in observational, theoretical, and modelling efforts. It will provide a platform to showcase cutting-edge research using state-of-the-art facilities. In addition to the groundbreaking observations from DKIST and SUNRISE, the session will draw on the latest results from missions like Solar Orbiter, Aditya-L1, and ALMA, laying the groundwork for analysing the wealth of data soon to emerge.

95 Insights into coronal Alfvénic waves from DKIST

Alfvénic waves form a key component on the Sun's atmosphere, found to be ubiquitous in the chromosphere, corona and solar wind. While not confirmed, they are believed to play a critical role in energy transport from the convective motions out into the heliosphere;
however, many open questions remain about their journey. The DKI Solar Telescope has started providing science quality data, with Cryo-NIRSP delivering high resolution (spatial, temporal, spectral) views of the corona in the infrared. During this talk I will
discuss several fundamental discoveries about Alfvénic waves that we have been afforded by the novel data from Cryo-NIRSP. Specifically, we show evidence that i) low frequency waves are the dominant energy carrier; ii) the waves are primarily excited by the
photospheric convection; iii) there are at least 3 separate sources for the waves, with evidence for the role of p-modes and an unknown source; iv) high frequency waves excited in the photosphere are strongly damped by partial ionisation in the chromosphere
before they reach the corona; v) the corona is replete with torsional Alfvén waves at small-scales. This list of discoveries provides observational confirmation for several theoretically proposed aspects of wave propagation. We also show that the torsional
Alfven modes carry a comparable amount of energy to the kink modes, indicating the Alfvénic modes carry enough energy to meet the heating and momentum budgets of the quiet Sun and solar wind.

96 Investigating Chromospheric Waves and Flows in a Giant Spiral Structure using SST CRISP.

Twisted magnetic fields in the solar chromosphere are thought to give rise to a plethora of MHD waves and flows, enabling mass and energy channelling from the photosphere to the corona. Here we report on the statistical properties of observations of waves and flows in an apparently stable but relatively large-scale spiral structure (herein referred to as a “giant spiral”), close to disk centre, in H-alpha 656.3nm line core images, from the Swedish 1-m Solar Telescope (SST) CRisp Imaging SpectroPolarimeter (CRISP) instrument. The observations are analysed using CRISPEX in conjunction with a loop tracing algorithm called OCCULT2, allowing us to trace 100s of magnetic loops forming the giant spiral. Extracted magnetic loops are then read into a new edge detection code to investigate the true nature of field aligned flows and waves. We are interested in the relation between loop curvature and the properties of the waves and flows. We report on the correspondence between hot signatures in the (E)UV images of the lower corona and high frequency waves and flows in curved loops in the chromosphere, using co-spatial and co-temporal observations in the (E)UV with observations taken from the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA).

Speaker: Yash Saneshwar (Northumbria University)

97 Identification of Nonlinear Damping of Transverse Loop Oscillations by KHI-induced Turbulence

Kink oscillations in coronal loops have been extensively studied due to their potential contributions to coronal heating and their role in plasma diagnostics through coronal seismology. A key focus is the strong damping of large-amplitude kink oscillations, which observational evidence suggests is nonlinear. Yet, nonlinear damping lacks a comprehensive theoretical interpretation. This work presents an analytic formula describing nonlinear standing kink oscillations dissipated by turbulence, characterised by a time-varying damping rate and period drift. We investigate how the damping behaviour depends on the driving amplitude and loop properties, showing that the initial damping time $\tau$ is inversely proportional to the velocity disturbance over the loop radius, $V_i/R$. Using MCMC fitting with Bayesian inference, an observed decaying kink oscillation is better fitted by the nonlinear function than by traditional linear models, including exponential damping, suggesting its nonlinear nature. By applying a Bayesian model comparison, we establish regimes in which nonlinear and linear resonant absorption mechanisms dominate based on the relationship between the damping rate $\tau/P$ and $V_i/R$. Additionally, analysis of two specific events reveals that while one favours the nonlinear model, the other is better explained by the linear model. Overall, our results suggest that this analytical approximation of nonlinear damping due to turbulence provides a valid and reliable description of large amplitude decaying kink oscillations in coronal loops.

98 Fine Structuring and Driving Mechanisms of Propagating Slow Waves in Coronal Fan Structures

Propagating slow magnetoacoustic waves, observed as intensity disturbances in extreme ultraviolet (EUV) emission, are powerful tools for magnetohydrodynamic (MHD) seismology. Their dispersive properties, phase speeds, and damping characteristics allow us to infer fundamental parameters such as temperature and magnetic field structure in coronal loops. Using observations from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO), we investigate the fine structuring and driving mechanisms of propagating intensity disturbances guided by field-aligned plasma non-uniformities in the corona. Our analysis focuses on sunspot-anchored coronal fan structures, referred to as “feathers,” within active region 13100, observed on September 19, 2022.
Through time-distance analysis, we identify propagating disturbances with three distinct periods, 3.06 ± 0.04, 2.47 ± 0.02, and 2.82 ± 0.02 minutes across three separate feathers, and projected phase speeds consistent with propagating slow waves. Enhanced chromospheric oscillations at corresponding periods, detected in the 304 Å channel at the umbral footpoints of these structures, suggest a direct coupling between chromospheric and coronal dynamics.
These findings provide new insights into the interplay between chromospheric and coronal oscillations and their role in energy transport across atmospheric layers. Additionally, these results highlight the potential of slow waves for coronal seismology, particularly in constraining magnetic field geometry. This work opens several new avenues for research in simulations, theory, and observations, particularly in further investigating the driving mechanisms of these waves and their role in coronal dynamics.

99 Uniturbulence and Alfven wave solar model

The heating of the solar corona and the acceleration of the solar wind remain unresolved questions in solar physics. Previous studies have primarily focused on Alfvén wave heating as the dominant mechanism, forming the basis of AWSoM models. These AWSoM models often require additional user defined processes to maintain a steady-state atmosphere. In this work, we explore kink wave heating as an alternative mechanism for coronal heating and solar wind acceleration, exploring the relative importance of Alfvén and kink waves.

The solar atmosphere is highly structured, exhibiting significant transversal density inhomogeneities. This leads to the MHD equations emitting a much richer spectrum of wave modes beyond the pure Alfvén wave. Unlike Alfvén waves, kink waves do not require counter-propagating components for turbulent energy transfer to occur. Instead, they undergo a process known as uniturbulence, enabling efficient energy dissipation and heating of the plasma.

To model the nonlinear turbulent dissipation of kink waves, we employ the Q-variable formulation introduced by Van Doorsselaere (2020). We implement this formulation within the Adaptive Mesh Refinement Versatile Advection Code (AMRVAC), allowing for high-resolution simulations of wave-driven heating in the solar atmosphere. Our preliminary results demonstrate that kink wave heating alone is sufficient to sustain a steady-state corona without requiring additional background heating terms. This marks a significant departure from previous solar wind models and provides a more physically motivated explanation for coronal heating and solar wind acceleration.

100 MHD Simulations of Cool Loop Formation and Kink Oscillation Dynamics in the Solar Atmosphere

We describe the formation of cool loops and the interaction of kink oscillations in coronal loop strands using magnetohydrodynamic simulation in ideal and non-ideal plasma regime. Firstly, we study the formation of cool loops using 2.5-dimensional MHD simulations in both adiabatic and non-adiabatic regimes. By implementing multiple transverse pulses resembling Alfvén pulses, we observe the non-linear transfer of energy and momentum to field-aligned perturbations through the ponderomotive force. This results in the creation of magnetoacoustic shocks and subsequent plasma motion, forming a cool loop system in the model solar atmosphere. We also examine the periodicity of flow velocity, applied Alfvén wave energy, and kinetic energy density along these cool loops, suggesting that impulsive Alfvén pulses can play a role in formation of cool loop and transportation of energy into the lower solar corona. Secondly, we describe the interaction of kink oscillations in strands of fine-structured cool coronal loops with field-aligned flows using 2-dimensional simulations under the ideal MHD regime. We investigate the influence of both uniform and non-uniform flow profiles on the characteristics of kink waves. We examine the excitation and attenuation of impulsively triggered fast magnetosonic standing kink waves, incorporating observed flow values by Hinode/SOT. We consider two types of inhomogeneity in longitudinal flow, varying in longitudinal and transverse directions. Our analysis under isobaric and isothermal conditions shows that the damping time decreases with increasing inhomogeneous flow width. The rate of damping-time reduction with respect to the half-width of flow is greater in unbounded flows compared to bounded flows.

Discovery in Astronomy and Space Physics enabled by large-scale Digital Research Infrastructures (ASTROCOMP)

Organiser: Nicholas Walton; co organisers: George Beckett, Louise Chisholm, Jon Hays, Anna Scaife, John Veitch, Mark Wilkinson

Computing and specialist technical skills underpin scientific exploitation across the Astronomy, UKSP, MIST community domains. STFC supports a range of infrastructures to enable High Throughput Computing (HTC, e.g. GridPP) and High Performance Computing (e.g. DiRAC). STFC’s IRIS (https://www.iris.ac.uk) digital research infrastructure (DRI) provides seamless access to these and other (e.g. The Hartree Centre, AIRR) resources.

This session will update the community on developments in IRIS and its partner infrastructure providers (e.g. DiRAC), highlighting the emerging scientific exploitation and data science opportunities opened up by access to massive scale computational and AI resources. Presentations will include examples of IRIS supporting gravitational wave analysis, large radio surveys (e.g. SKA), theoretical computational modelling, large optical imaging (e.g. Vera Rubin Observatory) spectroscopic surveys (e.g. 4MOST) and space (e.g. Gaia, Euclid, PLATO). The session will include discussion of how users can access IRIS resources through their particular project joining IRIS, providing detail on the opportunities to enhance their science.

The session will discuss the importance of enhancing research software engineer career paths and diversity in keeping the UK at the forefront of data exploitation. The session will also give the opportunity to discuss initiatives aimed at reducing the carbon impact of DRIs.

Early stage researchers, in particular, are encouraged to present their science enabled by use of IRIS facilities.

The session is organised by representatives of major projects involved in the IRIS initiative (https://www.iris.ac.uk/about-iris/partners/), and follows our successful AstroComp sessions that we have organised at the NAM 22, 23 and 24 meetings.

16:15 Prep time

101 The UKRI-STFC IRIS Research Infrastructure and Relevance to Astronomy

This presentation will discuss how the STFC IRIS digital research infrastructure is supporting a wide range of astrophysics projects. A status update will be provided, along with examples of use by projects such as WEAVE.

102 Developing the UK SKA Regional Centre

The UK Square Kilometre Array Regional Centre (UKSRC)
The Square Kilometre Array (SKA) is set to revolutionise radio astronomy. The SKA Regional Centre Network (SRCNet) will develop and deploy a collaborative and federated network of SKA Regional Centres, globally distributed across SKA partner countries, to host the SKA science archive and analysis services. The SRCNet will make data storage, processing and collaboration spaces available, while supporting and training the community, to maximise the scientific productivity and impact of the SKA.

The talk will provide an update on how the United Kingdom is playing a pivotal role in the development and testing of the SRCNet, as well as how we are working with the UK astronomy community to maximise the UK science return from the SKAO.

103 IRIS resources used at Cambridge for Gaia and PLATO data processing

At the University of Cambridge, hardware resources provided via the IRIS collaboration form an essential part in the data processing activity for two ESA science missions. For the Gaia mission, the core photometric processing recently migrated entirely to cloud infrastructure provided through IRIS. Using Apache Spark based distributed processing to characterize and calibrate the photometry and low-resolution spectra and generate the photometric and spectral data products for the upcoming Gaia DR4 catalogue. For the upcoming PLATO mission, aiming to discover earth-like exoplanets around solar-like stars, IRIS cloud resources are being used as the platform for the Exoplanet Analysis System which will be a key element of the on-ground processing.

104 Euclid UK Science on IRIS

The European Space Agency’s Euclid mission, launched to map the geometry of the dark Universe, aims to uncover the nature of dark energy and dark matter by measuring the shapes, redshifts, and clustering of galaxies over a third of the sky. Euclid’s Visible Imaging Channel (VIS) will provide deep, high-resolution imaging essential for precision cosmology.

The UK’s national computing infrastructure, IRIS, plays a critical role in processing and analyzing Euclid data, providing the computational power necessary to handle the mission’s unprecedented volume of observations. This infrastructure supports the development, validation, and application of scientific pipelines crucial to achieving Euclid’s ambitious science goals.

This presentation will highlight UK Euclid science activities conducted on IRIS, including:

Weak Lensing Galaxy Shape Measurement — Precise extraction of galaxy shapes for weak lensing cosmology, a key probe of dark matter and dark energy.

PSF Reconstruction Analysis — Accurate modelling of the point spread function to mitigate systematic errors in shape measurements.

Legacy Science Applications — Leveraging Euclid data for broader astrophysical studies, including strong lensing, galaxy formation, and galaxy cluster analyses.

This talk will emphasize how IRIS facilitates these science goals and accelerates progress towards realizing Euclid’s mission objectives.

105 The COSMA supercomputer for computational cosmology

We present the COSMA supercomputer which has a bespoke design optimised for computational cosmology. We discuss the ongoing hardware prototyping facilities and the access available for users, and likely future updates to this system, and how these will feed into the design of future COSMA systems.

106 AI Research Resource (AIRR) status and update

I will describe the current status of the UKRI AI Research Resource (AIRR)

https://www.hpc.cam.ac.uk/d-w-n

Enabling early science with Rubin LSST in 2025

Organisers: Graham Smith; co organisers: Steve Ardern, Astha, Michelle Collins, Thomas Cornish, Suhail Dhawan, Dimple, Paul Giles, Chris Lintott, Bob Mann, Garreth Martin, Steph Merritt, Mahdieh Navabi, Clara Pennock, Ana Sainz de Murieta, Jason Sanders, Matthew Temple, Roy Williams, Jacco van Loon

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will be a major pillar of the UK astronomy programme for the next two decades. Its unprecedented combination of spatial, spectral and temporal coverage enable it to probe a broad range of astrophysical phenomena, across all areas of astronomy, from near-Earth asteroids to distant quasars, the dark energy believed to drive the Universe’s accelerating expansion, and much more.

NAM2025 coincides with a major milestone of broad impact across the UK and international communities: the first release of on-sky Rubin data to data rights holders. These data have already been obtained during observations with the commissioning camera in late 2024. Science Verification observations with LSSTCam are also expected to be well underway in summer 2025.

In addition to the parallel session there is also a lunchtime session. We aim to encourage and enable the widest possible participation and engagement with the early data, with a particular focus on early career researchers.

We aim for a balance between five themes, across these five sessions:
o Introduction: Rubin/LSST, LSST:UK, and the international Science Collaborations
o Early career science: plans for early and future science with the Rubin data
o Tutorials and examples: how to access, filter, and manipulate Rubin data
o Community insights: technical and scientific preparations by LSST:UK researchers
o Engagement: an introduction to the LSST:UK engagement programme

In addition to talks from across the community, the sessions will include training, Q+A for early career researchers, a hack session, and a facilitated discussion.

Timetable_#62.csv

107 Vera C. Rubin Observatory and the Legacy Survey of Space and Time

I will give an overview of Rubin and LSST, including the current status of commissioning, the path to commencement of the survey, and the survey strategy.

Speaker: Federica Bianco (Vera C. Rubin Observatory)

108 Introduction to LSST:UK and UK involvement in Rubin/LSST

I will give a brief introduction to UK involvement in Rubin/LSST, through the LSST:UK Consortium and the STFC-funded LSST:UK Science Centre (LUSC) project. This will set the scene for the more detailed talks that will follow in the three sessions that we are running at NAM2025.

Speaker: Bob Mann (LSST:UK)

109 Introduction to early science with Rubin/LSST

I will give an overview of the eight Rubin/LSST Science Collaborations, and what data to expect when as commissioning is completed and the survey begins. The overall aim is to help people who are new to Rubin/LSST and LSST:UK orient themselves as they get ready for doing early science.

Speaker: Graham Smith (LSST:UK)

110 Lasair: the UK Broker for Rubin Alerts

Lasair is the UK Community Broker for transient alerts from the Legacy Survey of Space and Time from the Vera C. Rubin Observatory. I will explain the system’s capabilities, how users can achieve their scientific goals, and how Lasair is implemented. Lasair offers users a kit of parts that they can use to build filters to concentrate their desired alerts. The kit has novel light-curve features, sky context, watchlists of special sky objects and regions of the sky, dynamic cross-matching with catalogues of known astronomical sources, and classifications and annotations from other users and partner projects. These resources can be shared with other users, copied, and modified. Lasair offers real-time machine-to-machine notifications of filtered transient alerts. Even though the Rubin Observatory is not yet complete, Lasair is a mature system: it has been processing and serving data from the similarly formatted stream of the Zwicky Transient Facility alerts.

Speaker: Roy Williams (University of Edinburgh)

111 The ComCam Campaign and Data Preview 1

In my role as the LSST:UK's Production Scientist, I have worked closely with the Rubin Data Management Team during ComCam observations and running up to the release of Data Previous 1. I will provide a summary of the ComCam observing campaign, the key datasets released in DP1 and how to access them, and were to go to look for further information. If time permits, I will also summarise some of the work that has gone into ensuring a high quality DP1 deliverable.

Speaker: James Mullaney (The University of Sheffield)

The Role of Star Clusters in Star Formation from Local to Galaxy Scales

Organisers: Anne Buckner; co organisers: Ahmad Ali, Sean Linden, Hektor Monteiro, Steven Rieder, Christina Schoettler, Nick Wright

Star clusters are thought to be fundamental building blocks of our galaxy as most stars form in clustered environments of some sort. As such they provide crucial insights into the physics underpinning star formation from the local ISM to galaxy scales. For example, individual clusters are ideal laboratories to study stellar evolution and the mechanics of N-body stellar systems; while cluster populations can be used to trace galactic structure and investigate the physical processes of galactic evolution.

Unfortunately, the mechanisms of cluster formation, effect local and galactic environmental conditions have on this, as well as clusters longer term evolution,remain unclear. To better constrain them requires a multi-pronged analysis of (1) the internal structure and dynamics of the stellar and gas components of individual clusters; (2) cluster populations, comparing variation in their properties (age, mass, stellar composition) as a function of galactic environment and conditions.

This session will bring together a wide range of observers and modelers in the field of star clusters, from small-scale studies of individual clusters through to galaxy-scale population studies, to build up a cohesive picture of our current understanding of the critical role clusters play in star formation and the evolution of galaxies. We will focus the discussion around (1) new findings obtained using state-of-the art observations (e.g., Gaia & JWST) and simulations; (2) the best techniques/tools to effectively analyse and compare results from these.

112 The evolving view of the Galaxy through stellar clusters

Stellar clusters provide powerful probes of galactic structure and evolution, offering precise measurements of key astrophysical properties across a large volume of the Galaxy and covering much of its history. In this talk, I will discuss how advances in the cluster catalogue, driven by larger and higher-quality astronomical surveys and improved analysis methods, have reshaped our understanding of the Galaxy. Finally, I will highlight future research directions to advance galactic science through stellar clusters.

113 Spatial Properties of the NGC628 star cluster population

Examining the spatial properties of galaxies’ stellar and gas components provide crucial insights into the impact of galactic environment has on stellar evolution. Star cluster populations are ideal to study this issue, as they showcase how these properties vary with galactic position, evolutionary stage and mass. To this end, we have characterised the spatial distributions of star cluster population in nearby face-on grand spiral galaxy NGC628 using a combined JWST/HST catalogue and the statistical tool INDICATE. We have also - for the first time - directly compared the spatial behaviour of still embedded clusters with that of their natal clouds, made possible with our newly developed novel statistical tool CORRELATE. In this talk we will discuss our results, which suggest a scenario where the spatial distribution of the cluster population is influenced by that of the clouds, but is diluted and mostly erased over the next 100Myrs as clusters are fully disrupted or dissolved by stellar depletion, velocity shearing and/or gravitational interactions.

114 Star Clusters module in the Auriga Galaxy Simulations

Star clusters (SCs) are ubiquitous to most galaxies and are often used as tracers of galaxy formation and assembly. Their properties, e.g. metallicities, ages, spatial distribution, and masses, provide information about their formation environment. Understanding them at their birth, and subsequent evolution, is fundamental for their use as probes of galaxy evolution. Such understanding requires the cosmological environment, ideally from simulations, capturing the non-linear dynamics, internal and external, of the systems involved. However, modeling SCs in full cosmological simulations is challenging given the wide range of scales involved. Sub-grid or semi-analytic approaches have struggled to match observable counterparts, e.g. the Globular Cluster Mass Function (GCMF). In this work we present the implementation of a physically motivated sub-grid model for the formation and evolution of SCs in the Auriga galaxy simulation suite, that has been shown to produce realistic galaxies in the LCDM cosmological context. The formation of SCs is constrained to fully compressive media, and their evolution is shaped by their environment, as well as compact object remnants effects accelerating their evaporation via two-body interactions. We find that enhanced mass loss via two-body scattering from compact objects is critical to produce GCMFs compatible with observations (e.g. MW or M31), complementary to the findings of previous simulations with a similar treatment of the interstellar medium. This model is applied in the Auriga galaxy formation model at negligible extra computational cost making it ideal to make predictions for GC populations in a suite of MW-mass galaxies with a range of formation/assembly histories.

115 Investigating high-z star clusters with LYRA

JWST has recently revealed gravitationally lensed systems of high-z, star-cluster-like objects, such as the Cosmic Gems (z ~ 10.2) and Firefly Sparkle (z ~ 8.3). In this early epoch of galaxy assembly, these massive stellar clusters are thought to be the progenitors of present-day globular clusters (GCs). The emergence, early properties, and contribution to galaxy formation of GC-like objects in this era are, however, not well understood. To study these objects in a fully cosmological context, we utilize a cosmological zoom-in simulation of a Milky-Way-like halo using the LYRA model: an AREPO-based, ultra-high resolution (4 M_sun), multiphase interstellar medium implementation, featuring resolved blast waves of individual supernovae. Focusing on z > 8, we present the range of formation scenarios and resultant properties of the massive stellar clusters that are predicted by the simulation. We additionally compare the stellar clusters that form within the main galaxy to its satellite galaxies of similar stellar mass, and investigate whether it is possible to observationally distinguish them from one another. Finally, we put our findings in the context of JWST observations of high-z star cluster systems.

116 The Globular Clusters that Built the proto-Milky Way

Because they form their numerous stars so efficiently, globular clusters (GCs) have long been hypothesized to be the building blocks of young galaxies, with preliminary observations from JWST suggesting this may be the case at high redshifts. Within the Milky Way, our best tracers of the contribution of GCs to the proto-Galaxy are their most chemically peculiar stars: namely, second generation GC stars with such anomalous overabundances in nitrogen and depletions in oxygen ("high-[N/O] stars") that they can reliably be tagged as having originated in a cluster long after they have escaped. We identify associations between high-[N/O] field stars and Galactic globular clusters using their orbital integrals of motion and metallicities. These associations are compared to those between the rest of the halo and the GCs to quantify an excess association between the high-[N/O] stars and clusters, thus identifying the potential birth sites of the nitrogen-enhanced stars in the field. We find a strong degree of association with the low orbital energy, highest initial mass clusters, whereas such an association does not appear to strongly exist between the low energy clusters and high-[N/O] stars. This suggests that the most initially massive inner Galaxy clusters contributed a substantial number of the high-[N/O] stars in the halo–and confirms the in-situ origin of many of these stars. We propose that this link between these particular clusters and the nitrogen-enhanced halo stars exists because only in the inner Galaxy can the most massive clusters--which form the most second generation, high-[N/O] stars—be significantly stripped.

117 Fewer Companions in the Crowd: The Low Close Binary Fraction in Globular Clusters from Gaia RVS

In dense stellar environments like globular clusters (GCs), dynamical interactions are expected to alter binary properties, potentially disrupting or hardening close binary systems. Despite these expectations, the detailed comparison of close binary fractions between field stars and GCs remains underexplored. In this talk, I will present an analysis of the close binary fraction in a carefully selected sample of field stars and 10 GCs using Gaia Radial Velocity Spectrometer (RVS) data - the largest sample of GCs analysed using multi-epoch spectroscopy to date. By assessing the peak-to-peak variations of the sources’ radial velocity (RV) and modelling their dependence on the Gaia RVS magnitude, we can estimate the close binary fractions through a method that fits the distribution as the product of two Gaussian distributions. Our results confirm previous estimates of the close binary fractions in GCs and extend the analysis to additional clusters. Despite matching stellar parameters between the field and GC samples, our findings reveal that GCs possess a significantly lower close binary fraction compared to field stars. Interestingly, we do not detect any trend of binary fraction with cluster metallicity – metal-rich and metal-poor GCs are uniformly binary-poor. I will discuss possible interpretations, including dynamical hardening in dense environments and the effects of common envelope evolution, which may lead to companion accretion or merger events.

17:40 Poster Flash Presentations

The Golden Era of Gravitational Lensing: from Micro to Macro

Organiser: Maximilian von Wietersheim-Kramsta; co organisers: Aristeidis Amvrosiadis, Djuna Lize Croon, Leo Fung, Harshnoor Kaur, David Lagattuta, Samuel Lange, Gavin Leroy, Richard Massey, Nency Patel, Kai Wang

From the distortions of the images of stars due to exoplanets to the coherent warping of the relic radiation from the Big Bang, gravitational lensing (GL) is a phenomenon ingrained in the laws of gravity allowing us to probe astrophysics over a wide range of scales. Upcoming surveys, such as Euclid, Rubin LSST, SKA and Roman, will for the first time map weak GL over the whole sky from billions of sources. Simultaneously, instruments such as JWST, ALMA, ELT and HWO will observe strong GL with unprecedented resolution, while LIGO/VIRGO, LISA and IPTA can measure the impact of GL on gravitational waves. Truly, we are on the cusp of probing gravity, the nature of dark matter and the evolution of the Universe over untested regimes with unparalleled precision.

To mark this golden era in the field, we will bring together expert GL modelers, theorists, and observers to showcase and discuss their research. The session will focus on the scientific impact of GL probes: how they will inform novel theories, prepare the next generation of simulations, and improve data analysis techniques, while addressing current tensions. Through contributed talks, we will hear about a wide range of GL subfields with the aim of fostering collaboration and awareness within the field.

16:15 Welcome remarks

118 Stars as cosmic scales: measuring stellar mass with microlensed supernovae

Gravitational microlensing is a unique probe of the stellar content in strong lens galaxies. Flux ratio anomalies from gravitationally lensed supernovae (glSNe), just like lensed quasars, can be used to constrain the stellar mass fractions at the image positions. Type Ia supernovae are of particular interest as knowledge of the intrinsic source brightness helps constrain the amount of (de)magnification from the macromodel predictions that might be due to microlensing. We find that a sample of 50 well-modeled glSNe Ia systems with single epoch observations at peak intrinsic supernova luminosity should be able to constrain an average stellar mass-to-light ratio to within $\sim 15\%$. Much work is needed to make such a measurement in practice, but our results demonstrate the feasibility of microlensing to place constraints on astrophysical parameters related to the initial mass function of lensing galaxies without any prior assumptions on the stellar mass.

119 Gravitationally lensed stars and the stellar initial mass function at z~1 galaxies

We present a proof-of-concept study using lensed stars as a pioneer probe of the high-mass stellar initial mass function (IMF) at z~1 galaxies. Residing at cosmological distances, only the most luminous stars can be detected as a transient event even with the extreme magnification under the strong lensing effect from galaxy clusters and the microlensing effect from foreground intra-cluster stars combined. These luminous stars are consequently the most massive stars, the abundance of which is highly sensitive to the IMF and the star formation history (SFH). Assuming simple SFH models constrained by photometric measurements, we predict the transient detection rate in a lensed galaxy known as ``Spock’’ (z = 1) under different IMFs. With a Salpeter IMF, we can well reproduce the transient detection rate featuring young blue stars, as observed by HST and JWST. We found that the abundance of these young stars is very sensitive to the IMF and the most recent star formation rate, independent of the SFH model assumed. Given our methodology and assumptions, our Bayesian analysis thus infers that the observed transient detection rate prefers the “Spock” galaxy to have a Salpeter IMF instead of a top-heavy IMF, which would otherwise have overpredicted the transient detection rate significantly. With the many upcoming JWST imaging surveys, our proposed methodology can make use of the anticipated increasing amount of transients detected to potentially constrain the high-mass IMF of lensed galaxies, or even the IMF evolution throughout cosmic history.

Speaker: Sung Kei Li (The University of Hong Kong)

120 Quasi-periodic lensed light curves of stars by supermassive black hole binaries

Supermassive black hole binaries (SMBHB) form in galactic nuclei after galaxy mergers. In this presentation, I will demonstrate that inspiraling SMBHBs detectable with LISA may act as a binary gravitational lens leading to a new class of electromagnetic (EM) counterparts. The caustic (i.e. the curve on which the magnification diverges) of the binary lens is more complex than that of a single point mass, and the orbit and inspiral of the binary leads to the rotation and decreasing size of the caustic curve. This opens the possibility that a background source such as a star can cross the caustic multiple times during the binary orbital period leading to strong quasi-periodic time-dependent magnification. I will show examples where this EM signal may be detected, where the recurring peak magnification due to the SMBHB lens reaches a factor of 10^5 for giant stars with particular features which makes it possible to extract the properties of the supermassive binary such as the orbital period and eccentricity. These electromagnetic events may be targets for surveys such as LSST to identify inspiraling supermassive black holes even without a coincident gravitational wave detection.

121 Residual test to search for microlensing signatures in strongly lensed gravitational wave signals

When a gravitational wave signal encounters a massive object, such as a galaxy or galaxy cluster, it undergoes strong gravitational lensing, producing multiple copies of the original signal. These strongly lensed signals share identical waveform morphology in the frequency domain, enabling analysis without complex lens models. However, stellar fields and dark matter substructures within the galactic lens introduce microlensing effects that distort individual signals, making their identification computationally challenging within Bayesian frameworks. In this study, we propose a novel residual test to efficiently detect microlensing signatures by leveraging the fact that current Bayesian inference pipelines are optimized for the strong lensing hypothesis. Using cross-correlation techniques, we analyze microlensing-induced deviations imprinted in the residuals. Our simulations based on realistic microlensing populations show that while most events exhibit minor mismatches, a fraction have significant deviations. We find that 29% (56%) and 37% (69%) of microlensed events with mismatch > 0.03 and > 0.1, respectively, can be identified with O4 (O5) detector sensitivities, indicating that high-mismatch events are more likely to be discerned as microlensed. Considering the full population, our approach enables the identification of 12% (21.5%) of microlensed events with the O4 (O5) sensitivity.

Speaker: Eungwang Seo (University of Glasgow)

122 The Magnified Waltz: Simulating Light Curves of Binary Stars Passing through Micro-Caustics in Strong Lensing Galaxy Clusters

Individual stars located near the caustics of galaxy clusters can undergo extreme magnification when crossing micro-caustics, making them observable even at cosmological distances. Although most massive stars are likely to reside in binary systems rather than as single stars, the influence of binary star systems on magnification events remains severely underexplored. In this report, I will present our recent work on simulating the light curves of detached binary stars crossing micro-caustics to characterize their unique observational signatures. High-resolution magnification maps, generated using the GPU-PMO-CAUSTIC algorithm, combined with PARSEC stellar models to construct redshifted binary star systems, allow us to investigate the impact of binary star parameters and crossing geometries on microlensing magnification patterns.

Our simulations reveal diverse light curve features, including overlapping peaks, plateau-like structures, and time-variable color-magnitude differences. Notably, the distinct temporal variations in spectral energy distributions provide diagnostic tools for distinguishing binary systems from single stars, particularly highlighting the potential of multi-band photometry with the Chinese Space Station Telescope’s Multi-Channel Imager (CSST-MCI) to capture these variations. These findings offer theoretical support for identifying binary systems in future caustic-crossing events, contributing to a more precise characterization of high-redshift stellar populations.

Speaker: Wenwen Zheng (Chinese Academy of Sciences, Purple Mountain Observatory)

Active Galactic Nuclei – from ISCO to CGM and from cosmic dawn to the present day

Organisers: Carolina Andonie, Vicky Fawcett, Jiachen Jiang, Amy Knight, Amy Rankine, Matthew Temple

AGN are multi-scale phenomena, with interesting physics operating from the event horizon to the circumgalactic medium. In this session, we will bring together research on different aspects of SMBH accretion physics, AGN population studies, and AGN demographics. In this session we will cover:

Accretion discs, jets and outflows in the centers of AGNs. With the recent launch of Xrism and the ongoing success of existing missions, there is a wealth of data from high-energy telescopes. We will accept presentations of observational data analysis, observation-related numerical simulations, and theoretical research for this first session. We also encourage presentations of multi-wavelength and multi-messenger observations.

Obscuration in AGNs from both dust and gas, examining the accretion and host galaxy properties of different AGN populations such as obscured AGNs, red quasars, and HotDOGs. What can these different AGN populations tell us about the SMBH-galaxy connection?

Current and future large-scale surveys such as SDSS, 4MOST, MOONS, WEAVE, DESI, LSST, Euclid and LOFAR. These facilities will produce unprecedented samples of millions of AGN. With the UK taking a leading role in many of these projects, NAM is an excellent opportunity to examine the completeness of our AGN census, and the accretion, galactic and large-scale environmental properties of AGN across luminosity, stellar masses, and cosmic time.

123 Are dusty QSOs in a blow-out phase?

When we have an unobscured view of the accretion disc, which peaks in the UV, QSOs display very blue UV–optical colours. However, we have recently discovered a hidden population of QSOs, obscured by dust, which are almost completely uncharacterised by previous spectroscopic surveys. These dusty QSOs could represent an important short-lived transitional phase in the evolution of galaxies (a “blow-out” phase). Utilising data from DESI we can now, for the first time, explore a statistically significant sample of these reddened QSOs. Combining DESI spectra with radio data from the LoTSS DR2, we find a striking positive relationship between the amount of dust extinction and the radio detection fraction in DESI QSOs. This demonstrates an intrinsic connection between opacity and the production of radio emission in QSOs. In our latest study, we construct sensitive radio SEDs of 38 QSOs across 0.144-3 GHz frequencies, with additional ~kpc scale e-MERLIN imaging, in order to probe the origin of the enhanced radio emission in dusty QSOs. We find that dusty QSOs tend to display steeper radio spectral slopes compared to typical blue QSOs, which is likely due to outflow-driven shocks on the surrounding ISM. These results are consistent with dusty QSOs representing an important blow-out phase in the evolution of galaxies.

Speaker: Vicky Fawcett (Newcastle University)

124 Radio-AGN across the galaxy population: implications for fuelling and feedback

Active galactic nuclei (AGN) can have a significant effect on their host galaxies by regulating their growth or suppressing star formation (known as AGN feedback). Of particular importance for massive galaxies and clusters are jet-mode AGN which display powerful radio jets and keep galaxies ‘red and dead’ once quenched. However, until recently, the cosmic evolution of jet-mode AGN has remained largely unconstrained beyond z~1. The LOFAR telescope has been undertaking one of the deepest wide-field radio continuum surveys to date: this represents a novel sample to statistically study the evolution of AGN activity and feedback across cosmic time. Using this sample, I will present the first robust measurement of jet-mode AGN feedback out to z ~ 2.5. We discover a new dominant population of jet-mode AGN hosted by star-forming galaxies at high redshifts, that has not been previously observed. We find that the bulk of the AGN heating output is performed by this new population in the early Universe, highlighting their importance in early galaxy evolution. I will also present a detailed analysis of the host galaxy properties which finds evidence that this new class of AGN within star-forming galaxies is fuelled by a different mechanism compared to their quiescent counterparts. These results showcase the power of deep wide-area radio continuum surveys in characterising the nature of the faint AGN population across cosmic time.

125 The broad relationship between X-ray and radio luminosities for AGN

AGN activity is often revealed by strong X-ray and radio emission, even when the AGN is obscured at other wavelengths. Some AGN have been observed to be radio bright but X-ray faint, others X-ray bright but radio faint, as well as bright or faint/unobserved in both X-ray and radio. What determines whether the AGN will be X-ray or radio bright? Is it due to one mechanism that determines both, or two mechanisms in isolation, or even some mixture of the two? 

We use X-ray and radio data from fields (Bootes, COSMOS) that have been well observed, with large catalogues of multi-wavelength photometry and spectroscopy, to compare sources that that are X-ray and/or radio observed. We find that while X-ray and radio luminosities have a tendency to increase with redshift, we do not find any pattern between X-ray and radio luminosity at any given redshift. We also plot radio and X-ray luminosity functions for the radio and X-ray samples as a whole and compare them to the subset that is both X-ray and radio observed and find that there is a broad range of X-ray luminosity for a given radio luminosity range, and vice versa. This would imply that the instantaneous X-ray power, often a tracer of accretion, is not correlated with the radio power. However, there is an increase in the fraction of radio detected sources for sources with a more luminous X-ray detection, and vice versa, indicating a complex link between the X-ray emitting corona and the radio jet.

126 Simulated radio observations as a probe of fuelling and flickering in AGN jets

Simulations provide a way to connect observations from large-scale surveys of AGN jets to the evolution of these systems. This evolution is closely connected to the accretion process and fuelling physics, which is often variable on a range of timescales. We study this connection by conducting relativistic hydrodynamics (RHD) simulations using the PLUTO code. We use the Lagrangian particle module (Vaidya, B. et al. 2018) to track the energy spectra of non-thermal electrons, allowing us to more accurately predict synchrotron spectra and study the mixing of particle populations. We use these simulations to assess the applicability of spectral ageing models to radio observations and to search for markers of long-term flickering variability in accretion rate, as expected from chaotic accretion.

Estimating the ages of AGN is key to understanding the duty cycle and jet power of these systems. Our results suggest that periods of high jet power can lead to increased injection of energy into newly shocked material. This can reduce the apparent age of a source and lead to distinct patches of recently shocked material far back into the lobes. We find cases where relatively small changes in jet power mimic a restarting jet. We study the formation of knots along the jet due to recollimation shocks, with implications for high energy observations.

Overall, our results highlight the overall importance of jet variability for understanding the AGN jet population and show that synchrotron electrons could act as a unique probe of Myr timescale flickering in AGN.

127 AGN jets and wings: unravelling the mystery of cross-shaped X-ray emission

Jets from Active Galactic Nuclei have long been observed to interact with the interstellar medium (ISM). Such interactions provide possible mechanisms for star formation quenching, as required by cosmological simulations. The FRII quasar 3CR 14 (z=1.469) has been observed by Chandra to have significant X-ray emission to the southeast of the core, co-aligned with a southeast-northwest LOFAR-observed radio wing. Whilst FRII quasar 3CR 34 (z=0.69) and FRI radio galaxy 3CR 192 (z=0.05) both have significant X-ray emitting wings to the north and south of the core, perpendicular to their jets. Characterised as X-shaped galaxies, these AGN offer a unique investigation into feedback modes and jet-ISM interactions that can cause large sweeping filaments, jet associated hot spots and X-ray wings. 3CR 34 hosts all three structures with complex hot spot structures from jet-lobe interactions and a bow-shock-like filament cocooning the central galaxy and flowing into diffuse emission wings suggesting a blow-back mechanism. 3CR 14’s one-sided X-ray wing could be dominated by displaced gas heating as it falls back into the central galaxy.

Speaker: Tom Higginson (University of Bristol)

128 Unveiling AGN Outflows: A High Resolution Morphological Study with LOFAR-VLBI

How AGN (Active Galactic Nuclei) feedback operates is an unsolved mystery plaguing astronomy. AGN outflows could explain how this feedback operates. To investigate this, we use [OIII] as a tracer of ionised outflows. [OIII] has been connected to radio emission and with radio surveys deeper than ever before we can ask: What physical process causes this connection?

A unique instrument which can guide us closer to the answer is the International LOFAR Telescope (ILT). Using the LOFAR Two-meter Sky Survey Deep Fields at 144 MHz, I compare the [OIII] outflow properties and kinematics of 115 radio-detected AGN at z < 0.83 to 83 radio non-detected AGN. We discover 67% of radio-detected AGN host an outflow compared to 45% of radio non-detected AGN, indicating that radio-detected AGN are more likely to host an [OIII] outflow. We observe a stronger broad, blueshifted component in the radio-detected AGN, implying a profound link between low-frequency radio emission and [OIII] outflows.

To understand the origin of the radio emission, we harness widefield Very Long Baseline Interferometry (VLBI) processing and imaging by incorporating the international stations of the ILT into the data reduction process. These sub-arcsecond images give us crucial insight into the radio morphology, taking our understanding of the connection between [OIII] and radio to an exciting new level. I will present the first 0.3” resolution image at 144 MHz of the Boötes Deep Field and link sub-arcsecond radio morphologies to [OIII] outflows.

129 Comparing radio-loud Swift/BAT AGN with their radio-quiet counterparts

Some AGN are known to be efficient producers of strong, relativistic jets which power the extended radio sources. Largest and most powerful are the radio sources associated with AGN hosted by giant elliptical galaxies. Even among them, powerful jets are very rare phenomena and why this is so remains unanswered. Since relativistic jets are likely powered by rotating BHs via the Blandford-Znajek mechanism, the expected parameters deciding efficient jet production are BH spins and magnetic fluxes. If their values are large, the innermost portions of accretion flow should be affected by the jet production, which should be imprinted in their radiative properties. To verify this, we compare the radiative properties of radio-loud (RL) and radio-quiet (RQ) AGN selected from the Swift/BAT catalog with similar BH-masses and Eddington-ratios. We find that the only significant difference is the hard X-ray luminosities, which are about two times larger in RL-AGN than in RQ-AGN. This difference is speculated to come from RL-AGN having X-ray contribution from both the innermost, hot portions of the accretion flow and also a jet. However, this interpretation is challenged by our findings: (1) hard X-ray spectra of RL-AGN have similar slopes and high-energy breaks to those of RQ-AGN; (2) hard X-ray radiation is quasi-isotropic in both RL and RQ. We argue that the production of hard X-rays in RL is, like in the RQ, dominated by hot, central portions of accretion flows, while larger X-ray production efficiencies in RL-AGN can be associated with larger magnetic fields and faster-rotating BHs.

Speaker: Maitrayee Gupta (Astronomical Institute of the Czech Academy of Sciences)

130 Evidence to the jet powering mechanism in SDSS quasars from the LOFAR Two-metre Sky Survey (LoTSS)

A key component of AGN feedback is the injection of kinetic energy from radio jets. However, there’s a fundamental lack of understanding of why quasars, otherwise very similar, have such diverse radio jet powers and, therefore, the impact of AGN jets. Using large samples from LoTSS DR2 coupled with a Bayesian parametric model, we can separate jet from host galaxy radio emission, quantify the evolution of quasar jet power with properties including colour, black hole mass, and environment, and investigate the powering mechanism of radio jets across all energy scales. Our model reveals a positive correlation between weak AGN activities and quasar redness. We show that the traditional radio-loud/quiet quasar classification fails to reflect the physical origin of radio emissions in each population. Instead, our model allows for redefining radio quasar populations based on physical processes, which unifies previously divergent results and provides a coherent picture of how black hole mass impacts AGN jets. We show that a full range of jet powers is seen at all black hole masses, while quasars hosting the most massive black holes show an enhancement in radio emissions due to the higher incidence of powerful jets. We’ll present evidence linking the prevalence of high-power jets to stronger angular clustering and disc accretion mode of quasars. These results provide tight observational constraints on the launching mechanism of powerful radio jets in massive quasars. Finally, we will present preliminary results on the role of galaxy mergers in the triggering of radio jets utilising recent Euclid data.

17:35 Day 1 discussion and wrap-up

Information about session-related social events (TBC)

Star formation across environments: From individual molecular clouds to entire galaxies

Organisers: Eva Duran Camacho, Rebecca Houghton, Elizabeth Watkins; co organisers: Helena Faustino Vieira, Rowan Smith, Thomas Williams

Star formation (SF) is a fundamental process in the Universe, driving processes from the chemical and physical evolution of galaxies down to the initial conditions for planet formation. Local star forming processes, such as stellar feedback, and the larger galactic environment self-interact, altering star-forming conditions within individual molecular clouds and within galaxies globally. However, we still do not have a complete picture of SF across different scales and environments, from both observational and theoretical perspectives.

During this session, we will aim to:
o Link SF studies across different physical scales and environments (i.e. spiral arms, inter arms, galactic centres, and outer galactic regions).
o Improve cross-disciplinary discussions and encourage collaboration between observers and theorists.

The session will be divided into two blocks. The first block will explore resolved SF within individual molecular clouds and their connections to their galactic environment. The second block will provide insights on how galaxy evolution and galaxy-scale structures impact molecular cloud properties and SF within. Each block will consist of a 75-minute series of talks (1 review and ~4-5 contributed), followed by a 15-minute discussion on open questions in the field and how to address them, from both an observational and theoretical standpoint.

With facilities such as JCMT, ALMA, and JWST providing a wealth of new information both in the Milky Way and in nearby galaxies, this session will share the latest results across the star formation community and facilitate discussions between both simulators and observers working across different scales and environments.

131 Star formation and feedback on cloud scales in different galactic environments

Star formation is modified in molecular clouds by feedback from young massive stars. Pre-supernova feedback mechanisms are particularly important as they will set the stage for supernovae and the dispersal of energy out into the wider galactic environment, thus altering galaxy evolution. I describe how star formation and feedback can depend on galactic environment, for example for different gas surface densities and metallicities, and for spiral arms vs. inter-arm regions vs. galactic centres. I highlight how simulations are able to connect different physical scales using zoom-in simulations, going from galaxies to the interstellar medium. I also discuss how the relative impacts of different feedback mechanisms can be quantified from observations of real star forming regions, and how they can be interpreted using simulations and synthetic observations.

132 Emission line diagnostics in H II regions: a non-equilibrium perspective

Recent advancements in instrumentation have enabled the investigation of star-forming regions in nearby galaxies with unprecedented spatial resolution. To facilitate detailed comparisons between simulations and observations, we generate mock emission line maps based on a state-of-the-art simulation of an ideal H II region, utilizing a novel post-processing pipeline. This simulation couples radiation hydrodynamics (SWIFT-RT) with a non-equilibrium photochemistry network (CHIMES), incorporating 157 chemical species.
In this talk, I will introduce a new atomic model that accurately predicts hydrogen recombination line emissivity. This model is computationally efficient and can be seamlessly integrated into post-processing workflows for hydrodynamic simulations. By applying it to our new simulation, we gain new insights into emission line diagnostics in a non-equilibrium setting, which was previously unattainable. I will then explore widely used diagnostic tools in the ISM community, highlighting their deviations from traditional equilibrium-based predictions.
Our new atomic model and post-processing pipeline significantly enhance our ability to study emission line diagnostics from a non-equilibrium perspective. The atomic model, together with the pipeline, steps towards bridging the gap between simulations and observations, providing insights into the physical conditions of star-forming regions and contributing to the refinement of theoretical models.

Speaker: Yuankang Liu (Durham University)

133 Explaining the FUV--Hα SFR dichotomy in the M101 Group via HII region leakage

We examine the connection between diffuse ionized gas (DIG), HII regions, and field O and B stars in the nearby spiral M101 and its dwarf companion NGC 5474 using ultra-deep Hα narrow-band imaging and archival GALEX UV imaging. We find a strong correlation between DIG Hα surface brightness and the incident ionizing flux leaked from the nearby HII regions, which we reproduce well using simple CLOUDY simulations. While we also find a strong correlation between Hα and co-spatial far-ultraviolet (FUV) surface brightness in DIG, the extinction-corrected integrated UV colours in these regions imply stellar populations too old to produce the necessary ionizing photon flux. Combined, this suggests that HII region leakage, not field OB stars, is the primary source of DIG in the M101 Group. Corroborating this interpretation, we find systematic disagreement between the Hα- and FUV-derived star formation rates (SFRs) in the DIG, with SFR(Hα) < SFR(FUV) everywhere. Within HII regions, we find a constant SFR ratio of 0.44 to a limit of ~10^-5 M⊙/yr. This result is in tension with other studies of star formation in spiral galaxies, which typically show a declining SFR(Hα)/SFR(FUV) ratio at low SFR. We reproduce such trends only when considering spatially averaged photometry that mixes HII regions, DIG, and regions lacking Hα entirely, suggesting that the declining trends found in other galaxies may result purely from the relative fraction of diffuse flux, leaky compact HII regions, and non-ionizing FUV-emitting stellar populations in different regions within the galaxy.

134 The impact of different star formation models on galaxy evolution across cosmic time

Recent observational studies find that the star formation efficiency (SFE) per free-fall time varies both within and between galaxies. This strongly implies that galactic star formation (SF) might have additional physical dependencies beyond that on the gas mass/density implied by the Schmidt-Kennicutt relation. Yet this relation is often used to model SF in (cosmological-scale) simulations, missing out on nuanced differences that will affect each galaxy’s evolution due to the complex interplay between SF and feedback.

I will present detailed analysis of galaxies drawn from cosmological simulations, featuring different SF models: contrasting a constant SFE with one that takes into account the environmental dependence on the turbulent properties of the gas (which can successfully explain the observed star formation rate (SFR) of the Milky Way and the suppressed SFR in gas-hosting, early-type galaxies).

I will show that despite broadly similar stellar masses, the SFRs and SF histories differ significantly between the galaxies evolved with the different SF models. The gas properties (e.g. dense gas fraction, amount of fragmentation/interstellar medium (ISM) morphology) and thus the galaxies’ positions on scaling relations are distinctly different as well; a direct consequence of the different SFEs leading to SF in different ISM conditions, thus affecting the impact of the subsequent stellar feedback and further evolution of the galaxy. These results present an important step towards a better understanding of the physics of SF and the impact these small-scale processes have on galaxy evolution across cosmic time.

135 Magnetic Fields at the Heart of a ULIRG: Arp220

Arp220 is the nearest and brightest ultraluminous infrared galaxy and thus represents an ideal laboratory for studies of star formation in the extreme environment of a massive galaxy merger. Arp220, in particular, hosts star formation at a rate of ~100 solar masses per year, most of which takes place in heavily obscured molecular disks around the nuclei of the two merging galaxies. We here report the detection of polarised dust emission at submm wavelengths from the SMA from these nuclei, indicating the presence of magnetic fields that are roughly aligned with the molecular disks. These magnetic fields may play a role in suppressing feedback and promoting enhanced star formation rates and efficiencies, leading to the starburst behaviour of this galaxy. We also discuss the prospects for further observations of polarised dust emission in other local ULIRGs, and conclude that such studies may provide new insights into the details of extreme star formation environments.

18:00 NAM Football

18:00 Pre-public talk event activities

Members of the public welcome to see the Moon Palace, art and astronomy exhibitions, and a unique chance to see the RAS Bicentennial quilts

Public Talk (open also to participants)

136 Supernovae, Advanced Telescopes and the Search for Dark Energy

Over 25 years ago, two teams of astronomers discovered that the expansion of the Universe is accelerating.  This discovery was based on careful measurements of exploding stars, or supernovae, and the unexpected result earned the Nobel Prize for physics in 2011. However, the cause of the accelerating expansion remains a mystery. One explanation is that the universe is being pushed apart by some mysterious "dark energy", acting against the pull of gravity. In this talk, I will describe the work that led to the original discovery of the accelerating expansion of the Universe and the technological advances that made it possible. I will then describe the latest advances in observations of supernovae and some recent, tantalising results on the nature of dark energy. Finally, I will discuss the exciting prospects and challenges for the future as several new telescopes come into operation, including the ESA Euclid mission that is currently collecting data, the Vera C. Rubin Observatory that will soon begin observations, and the future European Extremely Large Telescope, which will be the biggest optical telescope in the World.

Speaker: Prof. Isobel Hook (Lancaster University)

Tuesday 8 July

08:00 Registration and set up

09:00 Moon Palace open to conference attendees

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Neutrino Multimessenger Astronomy

Organisers: Matteo Agostini, Anthony Brown, Teppei Katori, Ivan Martinez-Soler, Ryan Nichol

With their low interactional cross-sections, neutrinos are able to escape from dense and energetic astrophysical sources. As such, neutrino telescopes afford us a unique view with which to study the most extreme astrophysical events and particles in the Universe. The impact of this unique view can be multiplied if we employ it in a 'multi-messenger astronomy' approach to studying your favourite astrophysical topic. In this session we will look to cover the following topics:

o Neutrino telescopes (existing and future)
o Multimessenger astronomy with neutrinos
o Astrophysical neutrino sources
o Theoretical modelling of neutrino sources
o Interpreting neutrino astronomy observations
o Particle astrophysics with neutrinos

137 The Pacific Ocean neutrino experiment: new developments and physics case

P-ONE, or the Pacific Ocean Neutrino Experiment, is a future neutrino telescope to be operative in the northern hemisphere. It will be a multi-cubic kilometre detector offshore of Vancouver Island, British Columbia, and will utilize the world-leading infrastructure of Ocean Networks Canada. The first full line is set to be deployed by spring 2025 and will be followed by the demonstrator phase the subsequent year. The full detector is planned to be operative by the end of the decade and will be joining the newly constructed neutrino telescopes scattered across the world, pushing us into a new era of high-energy neutrino astronomy. In this talk we present the current status of the experiment and its expected performance, along with sensitivity studies focusing on the galactic centre and other discovery opportunities.

Speaker: Beatrice Crudele (UCL)

138 The Trinity PeV Neutrino Observatory

The Trinity Neutrino Observatory aims at detecting 1 PeV to 1 EeV tau neutrinos. We are developing the Trinity Observatory in three stages, of which the first stage, the Trinity Demonstrator, was deployed in Fall 2023. The Demonstrator serves as a pathfinder for the Trinity Observatory and informs the design of the first Trinity Telescope. In this talk, I discuss the status and first results of the Trinity Demonstrator and give a development update on the next stage of Trinity, Trinity One, which will be a premier instrument to observe neutrino point sources.

139 Unraveling Neutrino Properties with Neutrino Telescopes

The detection of neutrinos with energies above the TeV scale from astrophysical sources by neutrino telescopes has opened a new window for exploring the universe and testing the Standard Model at unprecedented energy scales. This talk will review recent observations from IceCube, including the detection of neutrinos from NGC 1068 and the more recent identification of neutrinos from the galactic plane, highlighting their implications for understanding neutrino properties across various scenarios. Given the long baselines and high energies of these neutrino events, we will focus on scenarios involving slow dynamical processes, which can significantly impact the observed neutrino signals.

140 Tau Neutrino Measurement Using the Track Sample in IceCube

The IceCube Neutrino Observatory identifies muon neutrinos through their characteristic long tracks, produced by high-energy muons resulting from charged current (CC) interactions. Similarly, approximately 17% of tau neutrinos interacting via CC interactions produce tauons that decay into muons, also leaving long tracks. However, the energy distribution between the hadronic showers and the muon differs between muon neutrino and tau neutrino CC interactions. By carefully reconstructing the hadronic shower energy (inelasticity), it is possible to statistically distinguish tau neutrinos from muon neutrinos. In this study, we analyze a low-energy IceCube track sample, covering the energy range of 500 GeV to 20 TeV, to search for tau neutrinos—potentially the lowest-energy astrophysical neutrino signals.

Speaker: Teppei Katori (King's College London)

141 Calibrating Molecular Cloud Density Tracers using Neutrino emission from the Galactic Centre

Firmly establishing the conversion of gas into stars within molecular clouds is central to understanding how galaxies build up their stellar populations. The efficiency and rate of star formation depend strongly on the properties of molecular clouds, especially their mass and density. While current models capture broad trends, many clouds within and beyond our Galaxy show deviations from the expected relations between star-formation rate and gas density. A major challenge in improving star-formation models is the large uncertainty in measuring molecular cloud masses. Traditional probes of gas density, such as dust or molecular line emission, often yield inconsistent results depending on local environmental conditions. This limits our ability to test star formation models with confidence. In this talk, we will show how the inner 200 parsecs of the Milky Way, the Central Molecular Zone (CMZ), is a natural laboratory to address this problem. It contains some of the largest and most dense molecular clouds in the Galaxy, often under a broad range of physical conditions. Its proximity to Earth also allows for high-resolution observations and the detection of weak high-energy gamma-ray and neutrino signals produced when cosmic rays interact with interstellar gas. Since the cosmic ray distribution in the CMZ is well constrained by gamma-ray data, neutrino emission provides an independent and unbiased probe of the gas density. This can be used to calibrate traditional gas tracers and reduce their systematic uncertainties, enabling more robust and reliable tests of star formation models, both within our Galaxy and beyond.

142 High-energy neutrino measurement at Super-Kamiokande and Hyper-Kamiokande

Super-Kamiokande observes a significant flux of upward-going high-energy muons produced by interactions of high-energy neutrinos. These neutrinos are useful for both particle physics and astrophysics, covering the energy region between accelerator-based experiments and neutrino telescopes. In this work, we utilize the upward-going high-energy muon sample to extract neutrino cross-sections in the TeV energy range using the Markov Chain Monte Carlo (MCMC) method. Additionally, we present a projection of the sensitivity of this physics for Hyper-Kamiokande.

Speaker: Nahid Bhuiyan (King's College London)

A holistic view of space sustainability

Organisers: James Blake; co organisers: Katherine Courtney, Stuart Eves, Robert Massey, James Osborn, Marieta Valdivia Lefort, Phineas Whitlock

The recent explosion in commercial activity in the near-Earth environment has paved the way for rapid growth and innovation in the space industry. Access to low Earth orbit is more affordable than ever, and consequently a diverse and expansive range of payloads are currently operating in the space domain. As humanity’s footprint in space continues to grow, the need for a comprehensive and sustainable approach to space exploration and utilisation has never been more pressing. In this session, we aim to examine a holistic view of space sustainability, integrating technical, governance and societal perspectives to address the short- and long-term impacts of current trends on both the space and terrestrial environment. How do activities in space support our quality of life, and why are they accelerating? What are the key concerns associated with this acceleration, across all stages of the mission lifetime of a spacecraft? How do we best mitigate these concerns to ensure safe and sustainable use of space, in light of latest developments in technology? What regulatory frameworks are needed to enforce responsible behaviour in the space domain, and how do we most effectively facilitate the global, cross-sector and interdisciplinary discussions necessary to ensure these frameworks are built on strong foundations of technical evidence. Importantly, what does the future hold for the space industry? We welcome contributions from the NAM community exploring the complex challenges of maintaining space as a safe and accessible domain.

143 Space Traffic Control - Are we just going round and round in circles, or can we achieve escape velocity?

Don Kessler sounded the alarm with regard to space debris as early as 1978, but the international reaction to his seminal paper has been disappointingly slow.
There is now a general recognition amongst space-faring nations that action to address the debris problem is necessary on a number of fronts: technical, financial, and legal initiatives are all urgently required.
This summary paper will examine the current status of Space Traffic Control, and will highlight the changes that have occurred over the past decade which have significantly increased the need for international cooperation in this area.
Routes towards a comprehensive solution will be suggested, involving contributions from space operators, national jurisdictions, and international bodies. A key principle of these proposals is that everyone should benefit from the system that is created.

144 Including Optical Astronomy in Space Sustainability Assessments

The term ‘space activities’ is a broad term that encompasses the use and exploration of the space environment by different users, whether these be satellite operators, astronomers, observers of cultural practises or others. The impacts of space activities also extend across many different Earth, space and human systems. Whilst some of these impacts are beneficial, others act counter to our definitions of space sustainability. As such, management tools are needed to reduce the extent of these negative impacts. To translate into effective management practises, these tools must be able to perform quantitative assessments of the impacts with respect to definitions of space sustainability. However, achieving this in a way that acknowledges the many diverse perspectives encompassed within space sustainability has not yet been realised at any level of space activity management. This work presents the model EMISSARY, a systems dynamics model which encompasses lessons from Earth-based applications of threshold-based methods for resource management. EMISSARY is a model designed to provide an understanding of the interconnections and trade-offs that exist between the multiple perspectives of space sustainability. With these insights, a holistic understanding can be gained of the impacts of space activities on the conditions within these broad and interconnected systems. In this paper, EMISSARY was used to illustrate how the needs of astronomers can be assessed in conjunction with the needs of other constituents of the space system.

145 Demonstration of a Portable Satellite Tracking System using Optical Parallax Measurements

With Earth's orbits set to become increasingly congested over the next several decades, the need for precise ephemeris of both active and defunct objects is crucial to ensure collision avoidance and the continued use of the space environment. Existing satellite tracking techniques have their advantages and limitations, including high costs, reduced precision at high orbital altitudes (radar), only detecting actively transmitting targets (antenna arrays), or the need for slow-moving targets (large telescopes). Recent advancements in COTS instrumentation, specifically CMOS sensors, now enable low-cost, high-cadence, small optical systems to be used for satellite tracking. We present a two-telescope system for photometry and precise, Kalman filter driven, orbital determination of space objects using parallax for range determination. An observation campaign was conducted in August 2024 on La Palma using a Planewave L350 direct-drive mount and a Celestron 11" RASA with a QHY600M CMOS, CLASP, a University of Warwick telescope. A twin portable system was designed with a custom-made mounting solution deployed on location to provide variable parallax baselines. Two distances of 2 km and 1.6 km were tested during three nights of observations, with over 250 targets ranging from LEO to upper MEO. With the use of parallax measurements, we derive both along-track, cross-track and range measurements. A novel processing technique for extracting the astrometry and photometry from highly streaked stars was created for image analysis.

146 Innovating for Infinity: Sustainable Technologies in Space

The rapid expansion of space activities has revolutionised technology and exploration but also poses significant sustainability challenges. Space debris, environmental impact, and inefficient resource use threaten the long-term viability of near-Earth operations. Emerging technologies offer solutions to these challenges, driving a shift toward responsible space practices.

This talk explores three key innovations in space sustainability: active debris removal (ADR), biodegradable satellite materials, and sustainable launch practices. ADR systems, such as NASA's ADRV and Airbus's RemoveDEBRIS project, use robotic arms, nets, and harpoons to capture and remove defunct satellites, reducing collision risks and preventing debris accumulation.

Next, biodegradable materials—like Japan's wooden LignoSat and ESA’s fiber-reinforced panels—offer an eco-friendly alternative to traditional satellite components, ensuring safe decomposition upon reentry without compromising durability.

Finally, advancements in sustainable launch systems, including reusable rockets by SpaceX and 3D-printed rockets by Relativity Space, significantly cut manufacturing waste and carbon emissions, making space access more sustainable and cost-effective.

By integrating these innovations with strong governance frameworks and interdisciplinary collaboration, the space industry can transition toward a circular economy, preserving the orbital environment and setting a precedent for responsible exploration beyond Earth.

147 The need to measure the mm sized dust flux in Low Earth Orbit.

The dust (up to mm size) flux in Low Earth Orbit (LEO) is a combination of natural cosmic dust and anthropogenic debris from spacecraft. As well as the threat of impacts on operational satellites from other satellites and defunct satellites, old upper stages etc., there is also a serious impact threat from such mm sized objects [1]. The contribution to the flux from space debris is held to be about to rapidly increase, yet there is a lack of data in this size regime [2]. It cannot be observed from the ground, so previous estimates were mostly derived by studying surfaces of spacecraft materials retrieved from LEO, searching for craters produced when dust impacted. But such retrievals are now rare. Hence, in-situ measurements are now required. The urgent need for new measurements and how they will require dedicated missions will be discussed.

Given current flux estimates, large detector surface areas will be required to produce annual estimates of the flux at the mm size scale, which will permit monitoring of the environment to see if it is degrading with time. Without the data from such missions, no informed debate on the hazard can be undertaken, and decisions will be made with minimal real input. Therefore new, in-situ, real-time measurements of the dust flux in LEO must be an important part of any strategy for sustainable space.

[1] Cornwell et al., Advances in Space Research, in press. 2025. https://doi.org/10.1016/j.asr.2024.06.058. [2] Wozniakiewicz and Burchell, A&G, 60(3), 38–42, 2019, https://doi.org/10.1093/astrogeo/atz150

148 RSO recovery through blind stacking – Current results and future goals

The safe and sustainable use of space requires a comprehensive understanding of the current populations of RSOs. However, the population of RSOs in Earth orbit is increasing rapidly, and while some of these objects are well characterised and tracked, a significant fraction of them have little to no tracking data. Often this is due to their small size which makes them difficult to observe via traditional means. To solve this issue, we require new techniques to better observe and characterise the population. In an attempt to better probe the small and faint end of the RSO population we have developed a blind stacking technique, designed to recover faint, moving targets in astronomical images. This technique is adaptable to any orbital regime and can detect moving targets from multiple orbits in a single dataset. Its key feature is that it can recover targets that are too faint for standard, single-frame extraction without requiring forehand knowledge of orbits. In this presentation I will describe the technique and highlight some of our current successes. The method has been evaluated on simulated data and has recently been positively applied to an INT dataset targeting GEO objects for which it has successfully improved the detection threshold. Additionally, I will discuss the potential improvements planned for the technique, including a more robust extraction of the orbital parameters of recovered targets.

Speaker: Benjamin Cooke (University of Warwick)

UK Solar Physics Open Session

Organisers: Natasha Jeffrey, Marianna Korsos, Matthew Lennard, Karen Meyer, Ryan Milligan, Rahul Sharma, Suzana Silva, Peter Wyper

The activity of our nearest star, the Sun, drives variability within the heliosphere in a myriad of different ways, impacting the Earth and other planets. As the only star on which we can begin to resolve physical processes at their intrinsic scales, the Sun provides a unique laboratory for plasma astrophysics. In this session, we welcome all contributions describing advances relating to physical processes occurring from the interior to the outer atmosphere, based on space- or ground-based observations, simulations, or theory. This session is open to all members of our community to present their work, irrespective of career level, including early-career researchers (PhD and postdoctoral).

09:00 Prep time

149 Flare evaporation, condensations, and ribbons

Evaporation and condensation processes are highly dynamic in solar flares, and both can be investigated through the chromospheric spectral lines and flare ribbons.

Evaporation occurs from a source of chromospheric flare ribbon material. The key mechanism(s) driving the evaporation are not neatly resolved, with plausible candidates including non-thermal beams of particles, field-aligned thermal conduction, Alfven waves, and reconnection outflow jets. We use state-of-the-art multi-dimensional MHD simulations to investigate differences in flare evolution that result from different energy transport mechanisms.

Condensations are seen in post flare loop arcades, with coronal rain events in which condensed material flows down towards the bright ribbons. We present the variations of flare ribbon spectral profiles using high-resolution spectro-polarimetric SST observations and sub-second cadence IRIS satellite spectra. These are used to track condensation flows and ribbon features. We also present so-called “chromospheric condensations” interpreting them through our multi-dimensional MHD models. We provide an updated schematic to interpret the formation of flare ribbons from the spectra.

Ongoing developments of our simulations are introduced: (1) improving the lower atmosphere used, and the initial reconnection location, (2) including asymmetry and more realistic chromospheric magnetic field parameters, (3) beam particle energy budgets and spectra informed by reconnection and particle acceleration modelling, (4) building a framework to estimate radiative energy losses and gains in the chromosphere from detail 1D RADYN models.

150 On the reliability of Local Correlation Tracking for inferring photospheric vortex flows in high-resolution observations

Vortex flows in the solar photosphere are ubiquitous and are thought to inject energy into the upper solar atmosphere in the form of Poynting flux. However, observing photospheric intensity vortices is challenging due to their small size and the fact that the flow field is primarily parallel to the plane-of-sky. Despite this, a large number of photospheric intensity vortices have been observed by applying Fourier Local Correlation Tracking (FLCT) to high-resolution observations. Validating these detections raises two questions: i) Are changes in photospheric intensity a suitable proxy for tracking the plasma velocity field? ii) Are the statistics on the observed properties of photospheric vortices accurate, given a significant number of vortices are considered to remain unresolved by most instruments? To address these questions, we compare observations from the Daniel K. Inouye Solar Telescope (DKIST) with a synthetic observation produced by a radiative magnetohydrodynamic MURaM simulation. We employ FLCT to infer the velocity field from the observations and use the $\Gamma$-functions method to identify and track the properties of vortices therein. We find a discrepancy between the number of vortices identified in the DKIST observation, the synthetic observation, and the plasma properties derived from the simulation. Here, we compare the simulated and inferred velocity fields and outline the potential implications of the validity of FLCT. This research draws important conclusions on the photospheric intensity vortices with further consequences on the expected energy transfer to the upper solar atmosphere.

151 Energy Fluxes in Reduced Magnetohydrodynamic Turbulence

Complex dynamics of a broad range of astrophysical, industrial plasmas and magnetofluids are well
described by the magnetohydrodynamic(MHD) equations.
However, due to this inherent complexity, further assumptions are often required to gain results with available resources.
A common feature of many plasmas is a strong magnetic field. One approximation that uses this assumption is called Reduced MHD(RMHD). This
model is described as a nonlinear, low-frequency incompressible approximation to 3D compressible MHD.
It correctly illustrates many known features of the strong mean-field limit of
MHD, but clearly cannot capture the full picture. It is unclear exactly how the RMHD
assumptions affect the transport of energy across scales, which dynamical processes are fully and correctly described and which are neglected. To identify the physical processes governing
turbulent energy cascades that are retained in RMHD, we leverage an energy flux
decomposition, that has recently been extended from hydrodynamics to MHD. This technique provides
a clear framework to identify the processes present in 3D incompressible MHD turbulence by splitting
the energy flux into subfluxes that originate from vortex stretching, strain self-amplification, current-sheet
thinning or current-filament stretching, and to quantify their contribution to the energy cascade.
The equations for the
MHD fluxes are expanded using the RMHD approximation. Leading order terms help to identify the main
processes in RMHD which are likely to be accurately modelled at this order, while higher order terms allow
an insight into the importance of neglected terms. We discuss
results for both high- and low-beta plasmas.

152 Determining distribution functions for collisionless current sheet equilibria: Analytical approach

Current sheets play an important role in many aspects of solar and space plasma activity. For example, a vast number of collisionless current sheets can be observed in the solar wind (e.g. Vasko et al., 2022). A common problem in the context of collisionless current sheets is having to find particle distribution functions which self-consistently generate a known magnetic field profile.

We shall present an analytical approach to this problem and will discuss examples in which the method works as well as others in which it fails.

Vasko, I., Alimov, K., Phan, T., Bale, S.D., Mozer, F.S., and Artemyev, A.V., 2022, ApJ 926, L19

153 Characterizing Flare-Associated Electrons with HXR Warm-Target and DEM Diagnostics

Understanding the properties and dynamics of energetic electrons in solar flares is critical for advancing our knowledge of flare energy release and particle acceleration. A key challenge lies in the fact that electrons of different energies are best probed by observations at different wavelengths. Hard X-ray (HXR) observations serve as powerful diagnostics for high-energy accelerated electrons, while EUV observations from AIA are sensitive to plasma below approximately 20 MK. Recent studies employing the warm-target HXR emission model in a kappa-form electron distribution, have shown that the accelerated electrons across the full energy range can be effectively constrained. In this study, we analyze two GOES M-class limb flares using both warm-target HXR model and differential emission measure (DEM) diagnostics to characterize flare-associated electrons. Our results confirm that the warm-target model can well constrain the flare-associated electrons when accounting for differences in thermal parameters derived from X-ray spectra compared to those from DEM analysis. Furthermore, DEM diagnostics offer valuable insights into the thermal environment of potential acceleration or injection sites. By comparing the DEM distributions with the mean electron flux spectra, we demonstrate that accelerated electrons represent only a small fraction of the total electron population within the flaring region. This study highlights the effectiveness of the warm-target model, when combined with DEM diagnostics, in capturing the key characteristics of flare-associated electron populations.

154 The Evolution of Secondary Mixed-Mode Instabilities beneath a Rayleigh-Taylor Unstable Prominence

Solar prominences are long, cool, dense features of the solar atmosphere. Within prominences, observations and simulations both show fine threadlike structures as mass collects within the magnetic dips. We study the formation and evolution of this mass falling under gravity beneath a dense prominence region through a less dense corona under the Magnetic Rayleigh-Taylor Instability (MRTI) in compressible and resistive 2.5D and 3D simulations using MPI-AMRVAC. We use high spatio-temporal resolution (order 10 km, 0.1 sec) to investigate the rise of secondary mixed-mode instabilities such as further Rayleigh-Taylor and Kelvin-Helmholtz instabilities along the leading edge of the falling RT knots, focussing on their initial descent through the corona. We compare the evolution of these secondary instabilities to mixing timescales and turbulent energy cascades across a range of field strengths and create synthetic observations to predict what can be seen by the Daniel K. Inouye Solar Telescope.

155 Improved atomic modelling for UV radiative transfer calculations

Radiative transfer calculations have been produced over the years for many lines and continua in the UV wavelength range of the solar atmosphere for a variety of conditions. Despite significant improvements in computing power and the availability of atomic data over time, atomic models are often still limited in size and rely on approximations for data. There have also been inconsistencies in the way photo-ionisation and radiative recombination have been treated. Here, we incorporate into the Lightweaver radiative transfer code new data and improved/new atomic processes. Data are taken from the CHIANTI database and other widely-available sources for the relevant elements. We show the significant impact this has on the UV continua in the 1100-1700Å region. The present treatment has important implications for radiative transfer calculations and the model atmosphere calculations used as inputs. If time allows, we will present new diagnostics we have developed for the solar chromosphere using lines in this wavelength region.

A multi-scale and multi-tracer view of the cosmic web

Organisers: Rita Tojeiro, Alyssa Drake, Meghan Gray, Andrew Pontzen, Tianyi Yang

The cosmic web is the characterisation of the matter distribution in the Universe into distinct environments – nodes, filaments, sheets, and voids – that are shaped by the anisotropic nature of gravitational collapse. Each distinct cosmic web environment has been shown to play an important role in the evolution of dark matter halos and galaxies via a variety of complex, multi-scale physical processes. The collective impact of these environments on galaxy and halo transformation is fundamental and diverse: for example, depending on scale, cosmic web environments can sustain galaxy and halo growth, but also inhibit it through stripping or tidal effects.

Our ability to study this impact is driven by rapid advancement of larger, denser, and deeper spectroscopic surveys alongside new generations of cosmological hydrodynamical simulations. We invite talks that consider the evolving anisotropic environment of galaxies and halos from the scales of the circumgalactic medium to that of massive clusters, and that trace the cosmic web via gas, galaxies, dark matter, or galaxy-CMB crosscorrelations. The goal of this session is to bridge research across scales and tracers, in simulations and in observations, such that the UK community can progress on questions such as:

o How do cosmic web environments influence galaxy and halo evolution across scales?
o How can cosmic web environments traced through different methods be compared?
o What links the anisotropic circumgalactic medium to larger-scale cosmic web structures?
o How do galaxies and halos transform as they traverse cosmic web environments?
o How does the cosmic web drive transformations over cosmic time?

156 How the Large-Scale Environment Impacts Galaxy Evolution: Feedback, Quenching, and Cosmic-Web Effects

The impact of the large-scale cosmic environment on galactic properties remains an open question in galaxy formation. While dark matter halos initially follow linear evolution, their subsequent growth is shaped by complex, non-linear interactions with their surroundings. Observational evidence suggests that proximity to large-scale structures, such as cosmic filaments, can induce quenching in galaxies, yet the underlying physical mechanisms remain unclear. In this talk, I will present a numerical experiment whereupon we make given Milky-Way-like halos form at increasing distances from a cosmological filament. This allows us to reveal that, while the mass and virial radius of the halos remain largely unaffected, their spin and shape orientation can vary by up to 80%, highlighting the strong influence of large-scale structures on their inner structure. By adding baryonic physics, and notably feedback, I will present how the large-scale environment affects feedback processes on small scale, shedding new light on the role of the cosmic web in regulating galaxy evolution. This reflects a differential accretion in the circumgalactic medium, which, in turn regulates gas inflows in the galaxy and ultimately star formation.

157 Local Group Analogs in a cosmological context: Relating the velocity structure to the cosmic web

The Local Group (LG), as a gravitationally bound system of the Milky Way and Andromeda, as well as their satellites, is a cornerstone of near-field cosmology. However, its utility as a cosmological probe requires understanding how it is related to the cosmic web. Using the ABACUSSUMMIT simulation, we identify LG analogues and quantify their environmental dependence. We find that the coupling energy of LG-analogue systems strongly correlates with large-scale overdensity, revealing a secondary bias effect. Crucially, we demonstrate that the LG-analogues are aligned to the anisotropic part of the cosmic web, and the alignment pattern is dependent on the coupling energy of the system. Our results underscore the role of non-local environmental effects in shaping LG-like systems and argue against treating the LG as an isolated system. Instead, we advocate for integrating the large-scale cosmic web into studies of LG analogues.

Speaker: Kai Wang (Durham University)

158 Probing baryonic feedback and cosmology with patchy screening in the FLAMINGO simulations.

Understanding the impact of baryonic feedback across different cosmic environments is crucial for accurate interpretation of large-scale structure in Stage-IV cosmological surveys. Hydrodynamical simulations offer a valuable tool for capturing how gas is redistributed by energetic processes, such as AGN feedback, and for predicting how this redistribution alters observable tracers of structure formation. Traditionally, feedback models have been constrained through X-ray and Sunyaev-Zel’dovich measurements of galaxy groups and clusters. However, new observational tracers are emerging that open up alternative windows into the baryonic content of the cosmic web.

One such tracer is the patchy screening effect, a subtle CMB anisotropy arising from excess Thomson scattering along the line of sight to groups/clusters due to their higher electron optical depths. This effect is sensitive to the diffuse baryons in the outer regions of the gas profile of the halo, tracing the structure of the cosmic web. It is complementary to the kinetic Sunyaev-Zel’dovich effect, as it probes optical depth without dependence on velocity.

In this talk, we present predictions of the patchy screening signal from the FLAMINGO suite of large-volume cosmological hydrodynamical simulations. By generating mock patchy screened CMB maps and cross-correlating them with simulated galaxy populations, we explore how feedback and cosmology shape the optical depth field. Our goal is to assess the sensitivity of this signal to the cosmology and baryonic physics, and to evaluate its potential as a new probe of the gas distribution within the anisotropic structure of the cosmic web.

159 The galaxy-environment connection revealed by constrained simulations

The evolution of galaxies is thought to be connected to their cosmic web environment. While environment is typically quantified using observed galaxy catalogues (e.g. using DisPerSE), this approach suffers from survey incompleteness and the uncertain relationship between visible galaxies and the dark matter backbone of the cosmic web.

Here we present the results of arxiv:2503.14732, where we use the CSiBORG suite of constrained simulations, designed to reproduce the actual large scale structure of the local Universe, to instead quantify environment using the underlying dark matter density field at the positions of observed galaxies. We define environment using both cosmic web position, identified by applying DisPerSE to the constrained simulation halos, and the local dark matter density (averaged on scales of up to 16 Mpc/h). We correlate these environmental measures with observed galaxy properties from optical (NASA-Sloan Atlas) and radio (ALFALFA) surveys. We robustly quantify statistical significance by exploiting both the Bayesian nature of the BORG algorithm, and using a supporting suite of unconstrained simulations.

We find significant correlations between environment and galaxy properties. Bluer, star-forming, HI-rich disk galaxies predominantly occupy lower density regions farther from filaments, while redder, elliptical galaxies with reduced star formation rates exist in higher density areas closer to filaments. Galaxy quenching shows similar patterns, with low-mass galaxy quenching demonstrating stronger environmental dependence than high-mass counterparts.

Notably, galaxy properties correlate more strongly with environmental density than with distance to filaments, suggesting local density exerts greater influence on galaxy characteristics than positioning within the larger cosmic web structure.

160 Identifying backsplash galaxies using machine learning

The evolution of galaxies is dependent on their present-day cosmic environment; whether the galaxies are isolated, or live in dense regions such as galaxy clusters. However, their evolution also depends on the environments they have experienced in the past. Backsplash galaxies are a key example of this -- galaxies that have previously passed through the centre of a galaxy cluster, but now reside in the cluster outskirts. These galaxies cannot easily be distinguished from those infalling for the first time, and so it is difficult to know whether to attribute galaxy properties in the cluster outskirts to the cluster itself, or to pre-processing en-route to the cluster.

Using The300 Project, a suite of hydrodynamical simulations of 324 galaxy clusters, we compare the properties of backsplash galaxies to those approaching a cluster for the first time. We develop a machine learning model, trained on these simulations, which is able to distinguish between backsplash and infalling galaxies based only on their present-day properties, with an accuracy of up to 90%. Crucially, this model only uses observationally measurable galaxy properties, such as their line-of-sight velocities and stellar masses, meaning it can be easily applied to real observations of galaxy cluster members to build pure samples of backsplash and infalling galaxies. This tool can therefore be used to disentangle different environmental effects, by better constraining the environmental histories of cluster member galaxies.

Speaker: Roan Haggar (University of Waterloo)

10:22 Poster annoucements

Active Galactic Nuclei – from ISCO to CGM and from cosmic dawn to the present day

Organisers: Carolina Andonie, Vicky Fawcett, Jiachen Jiang, Amy Knight, Amy Rankine, Matthew Temple

AGN are multi-scale phenomena, with interesting physics operating from the event horizon to the circumgalactic medium. In this session, we will bring together research on different aspects of SMBH accretion physics, AGN population studies, and AGN demographics. In this session we will cover:

Accretion discs, jets and outflows in the centers of AGNs. With the recent launch of Xrism and the ongoing success of existing missions, there is a wealth of data from high-energy telescopes. We will accept presentations of observational data analysis, observation-related numerical simulations, and theoretical research for this first session. We also encourage presentations of multi-wavelength and multi-messenger observations.

Obscuration in AGNs from both dust and gas, examining the accretion and host galaxy properties of different AGN populations such as obscured AGNs, red quasars, and HotDOGs. What can these different AGN populations tell us about the SMBH-galaxy connection?

Current and future large-scale surveys such as SDSS, 4MOST, MOONS, WEAVE, DESI, LSST, Euclid and LOFAR. These facilities will produce unprecedented samples of millions of AGN. With the UK taking a leading role in many of these projects, NAM is an excellent opportunity to examine the completeness of our AGN census, and the accretion, galactic and large-scale environmental properties of AGN across luminosity, stellar masses, and cosmic time.

161 Dust in shocks: The missing link in AGN feedback

It is well-established that shocks are the key driver for dust destruction in the interstellar medium (ISM). Feedback process from active galactic nuclei (AGN), such as winds and jets, can generate shocks that create harsh conditions where dust is expected to be destroyed.
Surprisingly, recent JWST observations show that dust grains and polycyclic aromatic hydrocarbons (PAHs) can persist in extreme environments (eg, high temperatures, fast winds) that favour grain destruction through sputtering and/or shattering. The processes underlying dust survival and processing in shocks remain poorly understood. In this talk, I will report on JWST/MIRI imaging of extended dust structures aligned with the narrow line region of a number of nearby AGN, where shocks are prevalent. Using simple models, I will demonstrate that not only does dust co-exists with shocks, but is also likely heated by them. To explore this further, I will present results from hydrodynamical simulations run with the Arepo code, to investigate dust survival under thermal sputtering in AGN-driven shocks. These simulations show that conditions such as grain size, shock velocity, gas temperature, and cooling efficiency can significantly influence the sputtering timescale. This has important implications for AGN feedback efficiency and the dust lifecycle, both of which are key to galaxy evolution.

162 The link between circumnuclear molecular gas reservoirs, millimetre continua and active galactic nucleus fuelling

Supermassive black holes (SMBHs) exist in almost all massive galaxies, and accretion of material onto these SMBHs is known to power active galactic nuclei (AGN). In this talk, I will the present results obtained by analysing ALMA data of a diverse sample of 35 nearby galaxies to study the link between circumnuclear (≤100pc) molecular gas reservoirs and AGN fuelling to better understand the powering mechanism. We find that the cold molecular gas mass within the nuclear regions does not correlate with any measure of AGN activity. This suggests that the AGN fuelling is not a ubiquitous process, even when cold gas is present. I will then discuss the origin of the nuclear mm emission in these sources. We find a strong relation between the nuclear mm emission from our galaxies and the SMBH mass, and an even tighter correlation is observed if the 2-10 keV X-ray emission is included. Classic torus models cannot explain the existence of the observed correlations, that we find instead naturally arising from advection-dominated accretion flows (ADAFs). This result suggests that radiatively-inefficient processes are ongoing in our sources (spanning a wide range of AGN types), and provides a new method to indirectly measure SMBH masses.

163 Evidence for universal gas depletion in a sample of 41 luminous Type 1 quasars at 𝑧 ∼ 2

Galactic feedback processes are thought to regulate the observed co-evolution of accreting black holes and their host galaxy that is observed across cosmic time. Since molecular gas is the fuel for star formation in these galaxies, it is crucial to analyse the molecular ISM properties to understand the impact of AGN/quasars on their host galaxy. Here I will present ALMA CO observations of a sample of 41 luminous unobscured quasars at z ~ 2 from the Sloan Digital Sky Survey (SDSS). All quasars in the sample have rest-UV to optical spectra tracing ionised gas in the broad line region (e.g. CIV) and the narrow line region (e.g. [OIII]), covering the full range of outflow properties in the SDSS quasar population at these redshifts. I will present the molecular gas properties including our findings on their gas fractions which are generally lower than both inactive galaxies and red quasars/HotDOGs at similar redshifts. This may suggest an evolutionary trend in gas fractions of quasar host galaxies, from obscured and gas rich to unobscured and gas poor. I will also present a tentative correlation between the measured gas fractions and the broad-line region properties with quasars showing high CIV blueshifts (indicating stronger broad-line region winds) having higher gas fractions.

Speaker: Stephen Molyneux (The University of Southampton)

164 Stellar populations of quasar host galaxies with Mean Field ICA

Co-evolution with active galactic nuclei (AGN) is extensively invoked to explain the properties of massive galaxies and the growth of supermassive black holes. Stellar populations and recent star-formation histories (SFHs), which can help constrain the processes involved in this co-evolution, are challenging to obtain for quasar host galaxies without special decomposition techniques. We use Mean-Field Independent Component Analysis (MFICA) to decompose quasar spectra and determine the stellar populations and SFHs of their host galaxies.

We apply MFICA decomposition to SDSS DR7 quasars (0.16 < z < 0.8), finding that quasars are hosted predominantly (~44% of our quasars) by star-forming galaxies and have, on average, younger stellar populations than a control sample of mass-matched galaxies. We also find that nearly 24% of our quasars are hosted by post-starburst galaxies – a significant excess (~10-20 times) compared to the fraction of post-starburst galaxies in the overall galaxy population. The heterogeneity of quasar hosts points to multiple feeding mechanisms, whilst the excess of massive post-starburst hosts points to the conduciveness of the post-starburst phase for quasar activity, possibly due to major mergers. Additionally, we compare our results to the host galaxies of Type-2 Quasars/AGNs, investigating if their hosts are identical (as per the unified model), or if they are distinct and follow a merger/obscuration-based evolutionary picture.

Speaker: Sahyadri Krishna (University of St Andrews)

165 The alignment of galaxies and AGN jets in the cosmic web environment

Active galactic nuclei (AGN) play a crucial role in the evolution of massive galaxies, but their fueling and feedback efficiency depend on the environment. In this talk, I will present a statistical study of the orientations of AGN jets and their optical counterpart in relation to the cosmic web environment. Using LOFAR Two-metre Sky Survey (LoTSS), DESI Legacy Imaging Surveys, and the SDSS cosmic filament catalogue, we find that galaxy optical major axes tend to align with cosmic filaments, suggesting the growth of galaxies through mergers along filaments. On the other hand, AGN jets, typically perpendicular to the host galaxy’s major axis, show more randomized orientations in cosmic filament environments. This supports a scenario where black holes in filament galaxies experience chaotic accretion as a result of numerous mergers. I will discuss the implications of these results in terms of the large-scale alignment of radio jets, intrinsic alignment of galaxies, and anisotropic quenching of satellite galaxies. Our results highlight the role of cosmic filaments in shaping AGN feedback and galaxy evolution.

166 Dissecting a Massive Quiescent Galaxy at z=4.7: The Role of AGN Feedback in Quenching Star Formation and Shaping Galaxy Kinematics

Recent JWST observations revealed a surprising number of massive quiescent galaxies (MQGs) at $z>3$. These systems formed and quenched extremely rapidly within the first billion years, which provides new constraints on how ejective AGN feedback can expel large amounts of cold gas from early galaxies.

We will present ultra-deep, spatially resolved JWST/NIRSpec IFU spectroscopy observations of GS-9209 at z=4.66, one of the earliest known MQGs. This galaxy hosts a dormant supermassive black hole (SMBH) and a ring of hot dust, likely due to past SMBH driven outflows.

However, this galaxy shows an ordered stellar rotation pattern, indicating a dynamically gentle quenching mechanism. The $\left(V/\sigma\right)_{R_{e}}=0.8 \pm 0.26$ ratio (smaller than typical high redshift star-forming discs) proves that ejective AGN feedback is likely responsible for the short quenching timescale of this galaxy. Powerful neutral gas outflows (with $\eta>10$, detected in NaD and Ca II H absorption) deplete the cold gas reservoir of this galaxy, maintaining it quenched. The high spin parametre $\lambda_{R_{e}} =0.66 \pm 0.10$ suggests that the AGN-driven quenching does not require an immediate change in the morphology and kinematics of early galaxies. The galaxy shows an infant central bulge, but its B/T ratio is smaller than the prediction of SHARK semi-analytical models. This further reflects a lack of major mergers in galaxy's history.

Using Jeans Anisotropic Modelling we constrain the dark-matter fraction of this galaxy, showing that it is heavily dominated by baryons, and we discuss our findings in the context of similar systems observed by JWST at lower redshift.

Speaker: Robert Pascalau (KICC, University of Cambridge)

167 Host galaxy physical properties of Euclid Q1 AGN

Measuring the physical properties of AGN and their host galaxies is key to understand their parallel evolution, particularly the correlation between the stellar mass and black hole mass.
Spectral energy distribution (SED) fitting is a powerful tool for extracting the physical properties of galaxies. However, hosting a bright AGN can dilute the host galaxy’s emission, biasing measurements by notably overestimating the host galaxy’s stellar mass.
Euclid’s unique photometric capabilities provide near-infrared photometry for an unprecedentedly large sample of AGN candidates, crucial for constraining AGN and host galaxy contributions and thus improving our physical parameter measurements.
I will present the AGN and host galaxy physical parameter catalogue for the Euclid Q1 deep fields: EDFN, EDFS, and EDFF. The novelty of my approach is the estimation of the reliability of the SED fitting measurements, resulting in a more robust catalogue for the users.
From the SED fitting outputs, I identify true AGN and compared this new selection with previous NIR (Bisigello+24) and MIR (Assef+19) color-color approaches. From the physical property differences, I demonstrate that these selection methods probe different AGN populations, and their combination provides a more comprehensive picture of AGN.
This work will be extended to the larger Euclid DR1 sample, offering a unique opportunity to investigate the AGN and host galaxy co-evolution by reliably determining their physical properties.

10:10 Poster Talks #2

Creativity: it’s good for you

Organiser: Lorraine Coghill; co organiser: Ged Matthews

Creativity is at the heart of astronomy, without it we wouldn’t be original, innovate and problem-solve, nor dream of unexpected connections or imagine truly big ideas. It is necessary within the process of research through both the small and large breakthroughs that take our thinking and ideas into the next phase. It can be a measure against group-think, challenge traditional thinking and contribute to better inclusion. It is identified as a key attribute of a researcher and yet creative thinking skills are not necessarily taught, highlighted or nurtured.

In this cross-disciplinary and interactive workshop space, we’ll explore creative thinking and consider how this critical transferrable skill can support our development not simply in our careers (our research, teaching and public engagement), but also within our everyday lives and personal wellbeing. We will investigate different models for creative thinking and discuss how we can lead and encourage creativity in others.

A ‘deconstructed’ panel of creatives from different sectors including science, the arts and education will actively share experiences and involve participants in aspects of their work helping us to explore and unlock creativity during the session. Contributions will come in a range of curious ways, and we invite participants to join in to share their ideas and creative responses.

Creativity it’s good for you - session info.docx

Timetable_#86.csv

Star formation across environments: From individual molecular clouds to entire galaxies

Organisers: Eva Duran Camacho, Rebecca Houghton, Elizabeth Watkins; co organisers: Helena Faustino Vieira, Rowan Smith, Thomas Williams

Star formation (SF) is a fundamental process in the Universe, driving processes from the chemical and physical evolution of galaxies down to the initial conditions for planet formation. Local star forming processes, such as stellar feedback, and the larger galactic environment self-interact, altering star-forming conditions within individual molecular clouds and within galaxies globally. However, we still do not have a complete picture of SF across different scales and environments, from both observational and theoretical perspectives.

During this session, we will aim to:
o Link SF studies across different physical scales and environments (i.e. spiral arms, inter arms, galactic centres, and outer galactic regions).
o Improve cross-disciplinary discussions and encourage collaboration between observers and theorists.

The session will be divided into two blocks. The first block will explore resolved SF within individual molecular clouds and their connections to their galactic environment. The second block will provide insights on how galaxy evolution and galaxy-scale structures impact molecular cloud properties and SF within. Each block will consist of a 75-minute series of talks (1 review and ~4-5 contributed), followed by a 15-minute discussion on open questions in the field and how to address them, from both an observational and theoretical standpoint.

With facilities such as JCMT, ALMA, and JWST providing a wealth of new information both in the Milky Way and in nearby galaxies, this session will share the latest results across the star formation community and facilitate discussions between both simulators and observers working across different scales and environments.

168 The ALMA Central molecular zone Exploration Survey (ACES): ALMA's multi-scale view of the CMZ

The Milky Way's Central Molecular Zone (CMZ) is a unique laboratory for studying astrophysical processes in an environment that is more extreme than typical star-forming regions in the Galactic disk. To understand the complex interplay between Galactic-scale processes and the small-scale physics of star formation, we have observed the entire CMZ as part of the ALMA Large Program 'ACES' (ALMA Central molecular zone Exploration Survey). ACES has observed the CMZ with all three ALMA arrays at 3 mm, covering a contiguous area of > 1000 square arcminutes down to spatial scales of ~0.1 pc. The survey's spectral setup includes key tracers (HCO+, HNCO, SiO, CS, H40α, etc.) that probe the physical, chemical, and kinematic conditions of the gas. The combination of high angular resolution and sensitivity across a large dynamic range provides the most detailed mm-wavelength view of the multi-scale structure of the CMZ to date. I will present an overview of ACES, and discuss how it promises to advance our understanding of key open questions, such as mass flows mechanisms, 3D structure, and whether star formation theories hold in this extreme environment. I will conclude by showcasing the finalised data products, which will soon be publicly released, along with highlights of ACES early science results.

169 What controls the star formation in Cloud E/F with ACES?

The Milky Way's central molecular zone (CMZ) presents an extreme environment for star formation, hosting the nearest supermassive black hole, young star clusters, and dense molecular gas clouds. Despite this rich environment, the CMZ perplexes astronomers by producing fewer stars than expected based on dense gas scaling relations. The ALMA CMZ Exploration Survey (ACES) aims to address this paradox and uncover the governing factors of star formation at the heart of the Milky Way by constructing a detailed, multi-scale picture of the physical and kinematic structure within the inner 100 pc of the Milky Way, down to individual star-forming cores using high-resolution and high-sensitivity ALMA data.

A key point of this multi-scale picture of energy cycling and feedback is understanding where the next generation of stars will form. Currently, we do not fully understand the specific conditions required for star formation in the CMZ, nor how these conditions may differ from those in the Galactic disk. To address this, I focus on Cloud E/F, a young supercluster progenitor cloud in the CMZ that shows signs of ongoing high-mass star formation. In my work, I investigate the kinematic properties of this cloud, focusing on the factors influencing star formation in such an extreme environment. My findings reveal sub/trans sonic gas motion providing new insights into the initial conditions for star formation.

170 Isolating the Central Molecular Zone using Fourier Filtering Techniques

Accurately determining the properties of the Central Molecular Zone (CMZ) poses a complex challenge for astronomers due to significant contamination from the Galactic Spiral Arms, through which we observe.

In position-velocity space, the CMZ is characterised by high-velocity spatially compact signals, while the Spiral Arms show low-velocity spatial extended signals. Considering this, we have developed a method utilising Fourier transform and filtering techniques to effectively separate these signals.

We apply these methods to the 12CO & 13CO J = 3 - 2 data obtained as part of the CHIMPS2 survey. By transforming the data to the frequency domain and applying band-pass filtering techniques, we isolate the distinct frequency components associated with the CMZ and Spiral Arms.

We present preliminary results to demonstrate the efficacy of our method in distinguishing between the CMZ and Spiral Arm signals, showing promise for enhancing our understanding of the structure and dynamics of these regions and allowing for direct comparison of their properties from single datasets. We also present preliminary estimates for several physical properties of the newly isolated spiral arms.

This method shows potential as a robust tool for astronomers to analyse complex galactic environments with distinct velocity features, and facilitates more accurate interpretations of observational data.

171 Magnetic fields in star-forming regions: recent results from the JCMT BISTRO Survey

The BISTRO (B-fields in Star-Forming Region Observations) Survey, a JCMT Large Program mapping Galactic star-forming regions with the POL-2 polarimeter, has constructed the largest extant sample of magnetic fields in star-forming region observed at sub-arc minute resolution. I will present a range of recent results from the survey, showing the similarities and differences between magnetic fields in a wide range of star-forming environments, from isolated prestellar cores, through low-mass filaments, massive infrared-dark clouds, to the Galactic Centre. I will discuss the evolution of magnetised molecular clouds to gravitational instability, and the emerging evidence for interactions between magnetic fields and stellar feedback across size scales.

172 BISTRO: Magnetic Fields Regulate Star Formation in the Western CMZ

The inner 100 pc of the Central Molecular Zone (CMZ) of the Milky Way is characterized by extreme conditions—high gas densities, vigorous turbulence, and strong magnetic fields—that differ markedly from those in the Galactic disc. Yet, despite this abundance of dense gas, the star formation rate is observed to be roughly a factor of two lower than that in the disc, which is a long-standing puzzle. In our study, we use the 850 μm polarized dust emission data from the JCMT BISTRO (B-fields In STar-forming Region Observations) survey, with a spatial resolution of 14.6″, to probe the magnetic fields in a number of molecular clouds located in the western CMZ (spanning a 0.3° × 0.2° area centered around (l, b) = (359.608°, –0.037°) between the 20 km s⁻¹ cloud and Sgr C).
Our analysis reveals that these clouds exhibit strong magnetic fields on the order of ~1 mG and are both magnetically subcritical and sub-Alfvénic. These characteristics indicate that magnetic fields provide significant support against gravitational collapse and turbulent compression. We, therefore, propose that the magnetic fields could play a dynamical role in stabilizing the molecular clouds, effectively suppressing star formation in these extreme environments. This magnetic field regulation may help to explain the observed low star formation

10:20 Poster Flash Presentations

10:30 Coffee Break

10:30 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

11:00 Annoucements

Plenaries 2 - Tuesday

173 Modelling Galaxies

Gaia and MUSE provide amazing data for both the Milky Way and external
galaxies. The data reflect huge selection effects and to overcome these we
need sophisticated chemo-dynamical models that can be `observed' with the
same biases. It's vain to suppose we can infer how galaxies formed and how they
work as machines until we have constructed credible chemo-dynamical models.

A chemodynamical model comprises a library of orbits with assignments of
stars or dark matter to each orbit such that the orbits' potential is jointly
generated by the stars and DM. The model doesn't need to be in equilibrium, but
equilibrium models are natural starting points - disequilibrium effects can
be modelled by perturbation theory.

Modelling requires a scheme for labelling orbits. Most current work follows
Schwarzschild in labelling orbits with initial conditons. This scheme is
highly non-unique and obscures the sampling density. The scheme is adapted to
the use of one pre-determined potential rather than a potential that emerges
from the modelling proces.

Orbits have natural labels - actions', which are constants of motion J(x,v) that can be embeded asmomenta' in a canonical coordinate system. The
canonically conjugate variables are `angles' w. An equilibrium model
comprises the DFs f_A(J) of various species A of star or DM. The model is
completely specified by the set {f_A} because the potential Phi(x) can be
computed from {f_A}.

The key to this approach is computing the mapping (x,v) <-> (w,J). The
Staeckel Fudge is a widely used map (x,v) -> (w,J). Torus mapping provides
the inverse map (x,v) <- (w,J) and recently we have shown that torus mapping
can also map in the direction (x,v) -> (w,J).

In a galaxy as in the solar system, resonant trapping and chaos are ignored
at a first pass but are crucial for secular evolution. We use perturbation
theory to understand these processes, and a key capability of torus mapping is
the provision of an intgrable Hamiltonian H(J) to which p-theory can be
applied.

Speaker: Prof. James Binney (University of Oxford)

174 Calculations of molecular spectra for astronomy

We can observe the Universe in exquisite detail by careful study of the wavelengths of light that arrive at Earth. However to interpret these signals requires laboratory data, much of it associated with spectroscopy and the behaviour of molecules. In hotter environments such the atmospheres of brown dwarfs, cool stars and most observed exoplanets, as well non-LTE environments such cometary tails, the amount of molecular data required can be huge. I will discribe efforts to provide the required information using detailed solutions of the equations of quantum mechanics from the detection of
H3+ in Jupiter's ionosphere to the ExoMol project, which aims to provide a comprehensive solution to this problem.

Speaker: Jonathan Tennyson (University College London)

12:45 Lunch

12:45 Meet the Editor (RAS)

RAS stall, TLC ground floor

12:45 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

WOMEN IN ASTRONOMY

Organisers: Ariadna Calcines Rosario, Mathilde Jauzac, Aurelie Magniez, Perrine Lognone, Meryem Dag

A networking lunch for all who identify as women in Astronomy. This session intends to facilitate connections and build community.

LSST and LSST:UK for Early Career Researchers

Organiser: Graham Smith; co organisers: Steve Ardern, Astha Astha, Michelle Collins, Thomas Cornish, Suhail Dhawan, Dimple, Paul Giles, Chris Lintott, Bob Mann, Garreth Martin, Steph Merritt, Mahdieh Navabi, Clara Pennock, Ana Sainz de Murieta, Jason Sanders, Matthew Temple, Roy Williams, Jacco van Loon

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will be a major pillar of the UK astronomy programme for the next two decades. Its unprecedented combination of spatial, spectral and temporal coverage enable it to probe a broad range of astrophysical phenomena, across all areas of astronomy, from near-Earth asteroids to distant quasars, the dark energy believed to drive the Universe’s accelerating expansion, and much more.

NAM2025 coincides with a major milestone of broad impact across the UK and international communities: the first release of on-sky Rubin data to data rights holders. These data have already been obtained during observations with the commissioning camera in late 2024. Science Verification observations with LSSTCam are also expected to be well underway in summer 2025.

At NAM2025 we aim to encourage and enable the widest possible participation and engagement with the early data.

This lunch session will be organised by and dedicated to Early Career Researchers, offering a selection of talks and other activities that are focused their needs and interests.

14:15 Moon Palace open to conference attendees

We've split the Moon Palace opening time entries to match timetable better*

Physical effects and multi-messenger signatures of energetic particles in galactic environments

Organisers: Ellis Owen, Kinwah Wu

Energetic particles, particularly hadronic cosmic rays, represent a significant fraction of the energy budget in many galaxies. They can deposit substantial energy and momentum within galactic media, influence galactic outflows and the circulation of baryons, and alter the thermal properties of the interstellar medium, potentially regulating long-term galaxy evolution.

Recent theoretical and observational advancements have improved our understanding of the role energetic particles play in galaxy evolution. However, the full implications of their complex, multi-channel feedback mechanisms operating over many decades in energy and across the full hierarchy of galactic structures are yet to be fully understood.

Energetic non-photonic particles are generated by cosmic ray processes in galaxies. They directly carry information about these processes, which are not always accessible through traditional photonic observations. Adopting a multi-messenger approach can therefore reveal crucial new insights about how cosmic rays engage with galaxies. With an upcoming new generation of high-energy multi-messenger and multi-wavelength observatories and experiments, it is timely to discuss how observational strategies and theoretical approaches can be aligned to promote the development of a complete picture of cosmic ray effects in galactic ecosystems.

This session will review the current state of our understanding of cosmic ray processes in galaxies. It will explore on their role in galaxy evolution, promote synergies between photonic and non-photonic domains, and highlight emerging opportunities within the broader context of multi-messenger astronomy.

175 Probing Jet Composition in Extreme Mass Ratio Black Hole Binaries through Periodic Emission Signatures

The composition of black hole jets—whether lepton-dominated or baryon-loaded—remains a longstanding open question, primarily due to the spectral degeneracy observed in high-energy emissions. We propose that extreme mass ratio (EMR) black hole binaries, particularly systems involving a secondary microquasar interacting periodically with the accretion flow of a primary supermassive black hole, can serve as natural laboratories for disentangling jet composition. In such systems, periodic jet–accretion collisions can give rise to distinct emission signatures shaped by underlying leptonic or hadronic processes. By modeling how these periodic features vary with jet composition, we identify multi-frequency observables that can help break the leptonic–baryonic degeneracy. These electromagnetic signatures offer a complementary probe to the emerging multi-messenger approaches for uncovering the nature of relativistic jets.

176 Unveiling the PeVatron: Neutrinos as Probes of High Energy Cosmic Ray Origins in the Galactic Centre

A decade of gamma-ray observations from the Milky Way's centre has provided hints of the existence of a Galactic accelerator, the so-called PeVatron, capable of generating cosmic rays up to PeV energy scales. These hints are based on the observation of a gamma-ray energy spectrum from the dense gas clouds at the centre of our galaxy, which follow an energy spectrum with no detected cut-off up to 100 TeV. The gamma-ray flux generated from these clouds also suggests a cosmic ray density that decreases inversely with distance from Sgr A*, indicating that the PeVatron is likely located in its vicinity. In this talk, we will discuss how neutrinos will become a fundamental probe to complement gamma-ray observations and shed light on the origin of these PeV cosmic rays in the future. This will be made possible through a combined analysis of the neutrino telescopes coming online in the next decade, as they will have the galactic centre in their field of view and achieve angular resolutions for muon neutrinos below a tenth of a degree. We will also explore what neutrinos can reveal about the point-like gamma-ray emissions in the galactic ridge region, whose origin remains under debate.

Speaker: Beatrice Crudele (UCL)

177 Neutrino as a new tool to characterise the Milky Way Centre

The Galactic Centre is a complex environment. It hosts many compact objects and the most massive clouds of molecular gas in our Galaxy. Neutral and charged pions are produced when cosmic rays from energetic sources collide with particles inside the molecular clouds. When the pions decay, the clouds glow in gamma-rays and neutrinos. Gamma-rays could be from other sources, but neutrinos are almost exclusively produced in hadronic interactions and are unabsorbed in propagations. They are thus unambiguous markers of hadronic processes. Observing these neutrinos will allow us to answer two of the mysteries about the Galactic Centre. One unresolved puzzle is the origin of PeV cosmic rays, and millisecond pulsars are considered one of the candidates. Another puzzle is the low star-formation rate of the molecular clouds at the Galactic Centre. In light of the development of the next generation of telescopes, such as KM3NeT, Baikal-GVD, and P-ONE, neutrinos will become a new tool for the study of the above problems. In this talk, we demonstrate how we can use neutrino observations to constrain the properties of Galactic Centre millisecond pulsars, as well as to trace the mass of the molecular gas.

Speaker: Paul Chong Wa Lai (Mullard Space Science Laboratory, University College London)

178 Probing the physics of cosmic ray transport in the multi-phase interstellar medium

The microphysics of cosmic ray (CR) propagation in complex, magnetized interstellar media remains unsettled. CR pressure gradients can self-generate magneto-sonic turbulence, promoting diffusion, while ion-neutral damping in dense regions suppresses this turbulence, favoring ballistic transport. The interplay between these processes across the hierarchical structure of the interstellar medium (ISM) governs how strongly CRs interact with different components of molecular cloud complexes, and determines their role in regulating the physical, thermal, and chemical evolution of ISM clouds. Recent gamma-ray observations and ionization rate measurements of nearby Galactic molecular clouds suggest that CR transport in dense clumps deviates from both purely ballistic and purely diffusive behavior. To investigate this, we present a self-consistent model of CR transport and interactions in magnetized molecular clouds, testing three CR propagation regimes: ballistic, diffusive, and a hybrid configuration featuring a diffusive envelope with a ballistic core. By computing ionization rates and gamma-ray signatures of CRs traversing parameterized cloud environments, we show that Fermi-LAT data and ionization measurements of nearby molecular cloud complexes are best explained by a combination of diffusive transport in turbulent envelopes and a transition to ballistic propagation in dense cores. Moreover, we find that the structure of the diffusive envelope must vary between individual clouds to consistently account for both the gamma-ray and ionization constraints. Our results establish an efficient new framework for interpreting multi-wavelength observations of CR interactions in molecular clouds and offer a path toward systematically constraining the physics of CR transport in dense ISM environments and its environmental dependence.

Speaker: Hayden Ping Hei Ng (ECAP/UCL)

179 An empirical microphysical determination of cosmic ray transport in the Gould’s Belt

Cosmic rays (CRs) influence the ionization, heating, and astrochemistry of interstellar molecular clouds. Their propagation through the complex structure of these clouds remains unsettled but appears to transition from diffusion in magnetized turbulent regions to ballistic streaming in dense cores. Efforts to characterize CR diffusion under varying physical conditions have produced a wide range of results. These studies typically rely on large-scale observable signatures to estimate an effective diffusion coefficient, but are not derived from the gyro-scale microphysics that fundamentally governs CR transport. As a result, it is difficult to disentangle CR propagation effects from other environmental factors that may influence the observed signatures. In this talk, we present a new method to empirically construct a diffusion coefficient for molecular clouds based on small-scale magnetic field properties. We use the angular dispersion function of 850 μm dust continuum linear polarization data to estimate the magnetic field strength, and apply a Fourier transform to extract the magnetic power spectrum. Together, these measurements provide sufficient information to characterize the propagaiton of CRs, grounded in the underlying microphysics. As a demonstration, we apply our method to JCMT observations of molecular clouds in the Gould’s Belt, enabling an estimate of the CR diffusion coefficient at tens of TeV. This work provides a first validation of the method and lays the foundation for future extensions to lower CR energies with higher-resolution ALMA data.

Speaker: Szu-Ting Chen (NTHU, ECAP)

180 Galactic Scale Bubbles in Galaxies - Beyond the Standard Leptonic Scenario

Recent observations indicate that galactic-scale bubbles are more prevalent than previously thought. Our Milky Way hosts the giant Fermi Bubbles, which are highly symmetric large gamma-ray structures emanating from the Galactic Centre and located both above and below the Galactic plane. The galaxy NGC 3079 also has galactic-scale bubbles, but they are considerably smaller than the Fermi Bubbles of the Milky Way. The structure and the emission of these bubbles seem to differ across galaxies. We speculate that galactic outflows such as those in the starburst galaxy M82 may be post-breaking-out phase of bubbles. In this unified scenario, the power of outflows driven by mini AGN jets and nuclear starbursts would be a continuous parameter, and some would fall within a certain range for a given galactic environment to exhibit a prominent bubble-like structure. While current literature strongly supports a leptonic spectral origin for the Fermi bubbles, a simplistic leptonic model is unable to accommodate the complexity of the environments and the bubble and flow dynamics for a spectrum of galaxies due to the constraint set by rapid cooling of leptons when compared to other relevant timescales, including the dynamical timescale of the host galaxies. We investigate a more general lepto-hadronic scenario by varying combinations of cosmic ray hadron and lepton densities and determine the dynamical evolution of these bubbles and the condition leading to its outburst to initiate the large-scale outflows. We present our model and the dynamical equations governing the bubble's dynamics, thus showing their different evolutionary stages.

181 Discovering Axion-like particles using Multi-band observations of Galaxy clusters

Axions or axion-like particles (ALPs) are hypothetical particles predicted by various BSM theories, which also make one of the dark matter candidates. If ALPs exist in nature, the CMB photons as they pass through galaxy clusters will convert to ALPs (of mass range $10^{-14}$ to $10^{-11}$ eV), resulting in a polarized spectral distortion in the CMB. The probability of the resonant conversion will depend on the mass of ALPs, photon-ALP coupling constant $g_{a\gamma}$, electron density and transverse magnetic field profiles of the clusters, as well as the photon frequency. If galaxy clusters are resolvable in various frequency bands, their astrophysical information can be obtained. We have developed a multi-band framework, SpectrAx, which uses radio synchrotron observations (say, with SKA), to obtain the transverse magnetic field profiles of clusters. Through X-ray observations (say, with eROSITA), their electron density and temperature profiles can be constrained. Using the spectral and spatial information of the CMB, the ALP signal from these clusters can be estimated. The clusters that are unresolved in various frequency bands, will create a diffused ALP background in the microwave sky. Such a signal will result in an increase in the CMB power spectrum at high multipoles, following the spectrum of the ALP signal. The two regimes will enable us to probe axions using the upcoming CMB experiments, such as the Simons Observatory and CMB-S4, which will be able to provide bounds ($g_{a\gamma}< 4\times{10}^{-12} \, \mathrm{GeV}^{-1}$) more than an order better than the current bounds from CAST ($g_{a\gamma}< 6.6\times{10}^{-11} \, \mathrm{GeV}^{-1}$).

Speaker: Harsh Mehta (Tata Institute of Fundamental Research, Mumbai)

UK Solar Physics Open Session

Organisers: Natasha Jeffrey, Marianna Korsos, Matthew Lennard, Karen Meyer, Ryan Milligan, Rahul Sharma, Suzana Silva, Peter Wyper

The activity of our nearest star, the Sun, drives variability within the heliosphere in a myriad of different ways, impacting the Earth and other planets. As the only star on which we can begin to resolve physical processes at their intrinsic scales, the Sun provides a unique laboratory for plasma astrophysics. In this session, we welcome all contributions describing advances relating to physical processes occurring from the interior to the outer atmosphere, based on space- or ground-based observations, simulations, or theory. This session is open to all members of our community to present their work, irrespective of career level, including early-career researchers (PhD and postdoctoral).

14:15 Prep time

182 Cool and hot emission disambiguation in (E)UV instrument passbands

Ultraviolet (UV) or extreme ultraviolet (EUV) passbands, despite being relatively narrow, typically include significant contribution from multiple ions, thus leading to mixed emission from widely despairing temperature formation regimes. This is particularly limiting for diagnostic purposes of the plasma temperature, where extreme cool/hot values in the solar/stellar coronae can be attributed to specific physical mechanisms such as magnetic reconnection or thermal instability. For solar observations, the ambiguity is particularly large when observing off-limb, where line-of-sight superposition is maximal and the diffuse, hot emission becomes comparable in intensity to that of clumpy, cool structures such as spicules, coronal rain and prominences. Recent work [1] has shown that the Response Fitting (RFit) method is particularly good and highly efficient in disambiguating the emission in the AIA 304 Å passband. This method is based on knowledge of the temperature response functions of the given passbands. In this work we further extend this method to other SDO/AIA channels and the IRIS/SJI 1330 and 1400 channels. We show that this method is generally very effective at isolating the cool, warm or hot emission, in both quiescent and flaring events.

[1] Antolin, P., Auchère, F., Winch, E., Soubrié, E., Oliver, R., Sol. Phys. 299, 94 (2024)

183 Constraining the Potential Field Source Surface Distance Using Coronal Tomography

The large-scale configuration of the coronal magnetic field is central to understanding the connection between the Sun and the solar wind, for forecasting space weather, and for interpreting both in situ and remote sensing observations of the corona and beyond. Potential field source surface (PFSS) extrapolations of the observed photospheric magnetic field are invaluable and have been widely used for several decades, but key parameters such as the distance of the source surface lack quantitative constraints. We investigated the use of tomographical maps of the plasma density in the extended corona, gained from coronagraph white light observations, as a constraint on the source surface distance. The values of the radial magnetic field component at the source surface are modified to allow a correlation with the tomographic densities. By adjusting the source surface distance, a maximum correlation is found at a particular distance, or a range of distances. The value of the maximum correlation gives a measure of the effectiveness of the procedure and is dependent on the quality of the tomography and PFSS results. Results for a number of dates over solar cycle 24 show evidence that the source surface distance is likely smallest at solar maximum around 2012 and increases with declining solar activity. Limitations of the method include the use of a purely spherical source surface, and the lack of correspondence between the information contained in the magnetic field data and the plasma density structure, which we try to address.

Speaker: Leigh Davis (Aberystwyth University)

184 Solar Active Region Nesting: Impact on Magnetic Activity and Coronal Structure

Magnetic activity varies over the solar cycle and is not uniformly distributed across the Sun’s surface; the latitudinal variation is clear from magnetic butterfly diagrams. Areas on the Sun with recurring flux emergence are called active region nests and show structure in longitude. These nests are thought to form due to non-axisymmetries in the generation and storage of the Sun's dynamo magnetic field. The nesting of magnetic activity is also observed on other Sun-like stars, suggesting that it is a fundamental process related to dynamo magnetic fields. However, our ability to study the long-term evolution and activity of solar active region nests is limited by their visibility from Earth. With ESA's Solar Orbiter periodically observing the Sun's far-side (akin to the STEREO-AB era), active region nests can now be studied in greater detail and over timescales of several solar rotations. Joint-observations of active region nests from the current solar cycle have shown that they produce more complex active regions (Hale classifications) with a higher occurrence rate of solar flares. Nested flux emergence also reinforces self-similar magnetic field topologies in the solar corona that can be leveraged when predicting the magnetic connectivity of spacecraft. In future, short to medium-term space weather forecasting will benefit from the improved identification and monitoring of active region nests.

185 Deep Learning study into sunspot evolution for use in flare forecasting.

Solar flares are large eruptions of electromagnetic radiation from the Sun that can affect the Earth's atmosphere and our technologies (e.g., radio communications). Flares are identified by the arrival of their energetic photons at Earth, meaning that their space-weather effects occur at the same time we become aware that a flare is in progress - this makes it essential for us to forecast them in advance. This work aims to predict solar flares within a 24-hour window using a Deep Learning model. We use 3D vectormagnetic images obtained from the Solar Dynamics Observatory (SDO) Space-weather HMI Active Region Patch (SHARP) data series, specifically the solar-radial component of the magnetic field. By using whole active region full-resolution images as input we want to improve our understanding of the physics leading up to flares and thus also improve forecasting accuracy. We use radial-field images from 2013 to 2023, inclusive, at a cadence of 24 hours along with the corresponding Geostationary Operational Environmental Satellites (GOES) X-ray flare events in the next 24 hours to create the image and flare-outcome label pairs. Filtering is performed to limit our data set to images containing single NOAA-numbered active region within ±75° longitude. With HARP separated data sets for training and testing, we implement a Fully Convolutional Network (FCN) for the binary classification of flare events with GOES X-ray flare class above C1. We present a statistical evaluation of the model’s predictive performance using various classification metrics, assessing its ability to distinguish between flare and non-flare events.

186 Impact of time-dependent WSA boundaries on solar wind properties in the heliosphere

Solar wind at L1 is modelled through a coupling of two independent and agnostic domains of the corona and heliosphere. The transition between the two domains occurs when the solar wind becomes supersonic and super-Alfvenic. The heliospheric solar wind is then be driven with appropriate boundary conditions at 0.1 AU which are derived from a coronal model. A popular choice for defining the boundary conditions using the Wang-Sheeley-Arges (WSA) model, which provides magnetic field from a potential model and estimates solar wind velocity through an empirical relationship with the coronal magnetic field.

However, while phenomena such as coronal mass ejections are time-dependent features, they are often simulated in a background wind that is quasi-steady and driven by a single WSA map or “snapshot” of the Sun. Such steady-state simulations don't capture the evolving nature of the Sun and discard information from previous time steps. In this study, we present results from a 2.5D magnetohydrodynamic (MHD) simulation of the heliosphere in the equatorial plane to assess the importance of incorporating the time-dependent boundary conditions on solar wind parameters in the heliosphere by driving simulation using time-evolving WSA maps.

We find that the movement of the heliospheric current sheet (HCS) around the equatorial plane drives reconnection, particularly during periods of high solar activity. We then inject monochromatic Alfven waves at the 0.1 AU boundary to study wave propagation in the heliospheric wind. Finally, we compare the forecasted wind parameters at L1 in a time-dependent simulation as compared to a steady-state simulation.

Speaker: Chaitanya Sishtla (Queen Mary University of London)

187 Quantifying what is lost in magnetic field modelling when using synoptic magnetograms

The evolution of magnetic flux on the solar photosphere is a highly dynamic process, featuring processes such as active region emergence, which can exhibit significant variability. Since these processes may occur on the far side of the Sun, our ability to construct accurate representations of the photospheric field for coronal modelling is constrained by the limited field-of-view provided by magnetograms taken from the Sun-Earth line. Here, we consider a magnetofrictional "ground truth" Reference Sun simulation spanning two solar cycles, that includes surface flux transport and bipole emergence. From this reference, we extract Carrington rotation maps (synthetic synoptic magnetograms) and use these to constrain the photosphere in limited-data simulations. Comparing these two studies reveals that the limited-data simulations significantly underpredict global quantities such as open flux and energy compared to the reference sun model. The spatial extent of footpoints of the open magnetic field is similarly underpredicted by models constrained by these synthetic synoptic magnetograms.

Speaker: Jonah Klowss (University of St Andrews)

188 Non-LTE Radiative Models of Coronal Condensations at Extreme Resolution

Radiation remains the primary vector by which the properties of solar plasma can be investigated. Atomic spectral lines, often forming in thin atmospheric layers, offer a powerful mechanism to probe the solar atmosphere, in particular its outer layers where conditions are typically outside of local thermodynamic equilibrium. Synthesising the radiation produced by numerical models also provides an essential lens through which to compare models and observations. Isolated solar structures such as filaments and prominences are of particular interest due to the complexity of spectral line formation within them and the diagnostic window this provides onto their formation and stability.

In recent years, magnetohydrodynamic models of these isolated structures have become significantly more advanced, whilst radiative treatments have primarily remained the same. We have recently introduced the DexRT code: a novel approach to multidimensional non-equilibrium radiative transfer using a technique termed radiance cascades to efficiently treat problems with intertangled layers of optically thin and thick material – a regime where current approaches can fail with dramatic so-called ray effects. Here, I will present spectra from a variety of lines synthesised from detailed multidimensional magnetohydrodynamic models. I will also discuss the importance of considering both detailed radiative transfer and viewing angle effects when making predictions and comparisons to observations.

Speaker: Christopher Osborne (University of Glasgow)

SETI – The Search for Technosignatures, Biosignatures and Beyond…

Organisers: Louisa Mason, Kelvin Wandia, Michael Garrett, Andrew Siemion

The search for extraterrestrial intelligence (SETI) has profound implications in our understanding of the abundance of life and our place within the universe. An increasing number of telescopes – Green Bank, Parkes, Very Large Array, MeerKAT, e-MERLIN – are dedicating time and resources to the goal of finding evidence of intelligent civilisations, known as technosignatures. One of the key science goals of the upcoming Square Kilometre Array (SKA) will be SETI, under The Cradle of Life Working Group.

SETI has largely focused on radio and optical frequencies, with newer methods targeting infrared waste heat leakage. AI and machine learning are increasingly applied to detect anomalies in large astronomical data sets. With the Breakthrough Listen Initiative now based in Oxford and its collaborations with Manchester and other UK universities set to grow, this is the perfect moment for a SETI session at the NAM.

This session will aim to explore techniques in technosignature detection, surveys and telescopes employed to search for extraterrestrial life as well as current and future surveys in exoplanet & biosignature detection. Discussion on strategies to explore the ‘Cosmic Haystack’ across space, frequency and time will promote collaboration in our efforts to detect technosignatures. The overall goal will be to demonstrate UK contributions to the field and expand the national community.

14:15 Prep time

189 Keep Listening and Carry On: Breakthrough Listen in the UK

Breakthrough Listen, the planet's most comprehensive search for technosignatures, was launched in 2015 at the Royal Society in London. In 2023 the project returned to the UK in earnest, with a move of its global headquarters to Oxford, as well as partnerships across the country. Listen engages with observing facilities and research groups around the world, gathering unprecedented volumes of data in the search for technosignatures.

By leveraging expertise in digital signal processing, algorithm development, machine learning, and cutting-edge hardware, Breakthrough Listen is placing the strongest constraints to date on the presence of intelligent life beyond Earth. Strong synergies with other science areas have also enabled Listen to contribute to other topics in astrophysics including fast transients, stellar flares, the search for interstellar objects, and constraints on dark matter.

This talk will provide an overview of the program as well as discussing opportunities for partnership with UK scientists - in particular, students and early career researchers.

190 The opportunities and challenges of using near-infrared high-resolution spectroscopy to detect atmospheric technosignature gases in exoplanets

The search for atmospheric technosignature gases using high-resolution spectroscopy in the near-infrared is a valuable extension of the search for general biosignatures and low-abundance gases in exoplanet atmospheres. High-resolution cross-correlation spectroscopy (HRCCS) is the best technique currently available for this, since it can disentangle faint potential technosignatures from features of more significant atmospheric constituents, such as H$_2$O, and use the light-collecting power of the Extremely Large Telescopes. My research explores the viability of searching for technosignature gases with next-generation, high-resolution spectrographs, such as METIS/ELT, setting realistic expectations on the likelihood of being able to detect these gases on nearby exoplanets, as a function of their concentration. In this talk, I will present a simulation pipeline that can model retrievals of technosignature and other low-abundance gases on rocky exoplanets with the ELT. I use this pipeline to simulate a search for sulphur hexafluoride (SF$_6$), which has potential to exist as an industrial pollutant, and as an intentionally released artificial greenhouse gas on planets with insufficient natural CO$_2$ production. SF$_6$ is nontoxic, relatively chemically inert, and has an atmospheric lifetime of ~1000 years, making it a prime technosignature target. During this talk, I will demonstrate the challenges in HRCCS that need to be addressed for this technosignature search, including the required spectral resolution and light-collecting power, the availability of detailed and accurate line lists, and the trade-offs between wavelength coverage and background thermal noise, when considering observations from ground and space e.g JWST, the ELTs, and the Habitable Worlds Observatory.

Speaker: Mitchell Yzer (University of Oxford)

191 Stellar transients, space weather and SETI with the SKA

SKA precursors and pathfinders are discovering novel transients across an immense range of astrophysical regimes - from flare stars to FRBs. I will discuss recent serendipitous and untargeted discoveries of a range of stellar transients made possible by repeat sampling of wide parts of the sky by both the MeerKAT and ASKAP telescopes, revealing a diversity in stellar radio astronomy and a wealth of active and dynamic stellar systems in our Galaxy. I will demonstrate how the resolution and sensitivity of the precursors and later the SKA itself are crucial for detecting these transients at scale.
Discovery and follow-up of these stellar radio bursts gives crucial insight into the magnetospheres of stars and the space weather in their environments. To date there have been very few confirmed solar radio burst analogues that are correlated with space weather effects. Furthermore, the prevalence and effects of such space weather are a crucial piece of the puzzle to investigating the abundance or dearth of life in the Universe. I will discuss ongoing searches for technosignatures with SKA precursors, how these searches may be affected by such stellar activity and what these observations imply for the habitability of any hosted exoplanets. Finally, the sensitivity of the SKA will allow for the first searches for non-directional leakage radiation from the nearest star systems for the first time and I will discuss how targeted and commensal observing strategies will be able to place the tightest constraints on one of the most fundamental questions in science.

192 Phosphine in Venus’ Clouds - local biosignature experiences

We present new results from the JCMT-Venus programme and other observations looking at potential biosignatures in the clouds of Venus. JCMT-Venus is a JCMT long term programme to monitor the atmosphere of Venus at millimetre wavelengths to determine the presence and abundance variations of a variety of molecular species over day to year timescales. Three roughly month long observing campaigns were undertaken in Feb 2022, July 2023 and September 2023. The main target molecular species are HDO, SO2 and PH3, phosphine, which is a proposed exoplanet biosignature and whose presence has been argued as a potential sign of life in the clouds of Venus. We will describe the new JCMT-Venus results and their implications for the presence and behaviour of phosphine on Venus. The detection of phosphine on Venus has been controversial and so it makes a useful case study for the detection of biosignatures elsewhere. We also present the first results from observations in the cm wavelength range in search of other potential disequilibrium molecular species which might have further implications for the possible existence of life in the clouds of Venus and for biosignature searches elsewhere.

193 Examining Airport Civilian and Military Radar Leakage as a Detectable Marker for Extraterrestrial Civilizations

We present comprehensive simulations of Earth's radar systems as potential technosignatures detectable by extraterrestrial observers. While SETI has traditionally focused on deliberate transmissions, we examine unintentional electromagnetic leakage from civilian airport radars and military radar systems. These technologies, essential to any advanced civilization's infrastructure, produce significant radio emissions that may be detectable across interstellar distances. Our study implements a cosecant squared beam model for civilian radar and a phased array beam simulation for military systems to realistically characterize their emission patterns. We analyze how the global distribution of radar installations affects the temporal structure of Earth's radio signature when observed from six specific stellar systems: Barnard star, HD 48948, HD 40307, AU Microscopii, HD 216520, and LHS 475. We demonstrate how a planet's infrastructure deployment significantly influences the detectability and characteristics of its technosignatures. The results reveal distinct patterns in radio leakage that depend on both terrestrial radar distribution and observer location, providing valuable insights for future SETI strategies. Our findings suggest that radar systems, represent among the most detectable unintentional technosignatures of technological civilizations, offering a promising avenue for extraterrestrial intelligence detection.

194 Micron Scale Technosignatures: How Examination of the Lunar Regolith may Constrain the Number of Past Technological Civilisations in the Galaxy

The plausibility of micron-scale transport from the Interstellar Medium through the heliosphere has been affirmed by discoveries of interstellar dust particles in the Solar System. Both the intentional and unintentional dispersion of micron-scale debris from anywhere outside the Solar System might also enter it, at hyperbolic velocities, and potentially offer evidence of other technological civilisations. We present analyses of the potential sources, quantities, and discoverable proportions of micron-scale extraterrestrial artefacts on the Moon and other stable surfaces in the Solar System, transported by stellar winds, radiation pressure, and other natural processes. These include accidental releases from host systems that may be thrown out by collisional cascades in large techno-structures (e.g. Dyson spheres/swarms), then ‘ground to dust;’ long-lasting solar sails pushed out of their host star orbits as they ascend the main sequence or red giant branch; and gravitational slingshots of artefacts by large planets. For both accidental and deliberate dispersions of micron-scale particles we examine possible survival rates through the hot, warm and cold ISM. We introduce the computer vision and machine learning tools that may lead to their detection, both directly and by way of their hypervelocity impact crater morphologies, as well as to the detection of any macro-scale constructions that may have been designed and programmed to develop from such particles, taking advantage of the same natural transport processes. Finally we introduce scenarios by which these detection mechanisms, with examination of varying volumes of the lunar regolith, may constrain the number of past technological civilisations in the Galaxy.

Speaker: Dr Lewis Pinault (SETI Institute, UCL/Birkbeck Centre for Planetary Sciences)

195 Anomaly Detection in Green Bank Telescope SETI Data Using Deep Autoencoder Latent Spaces

Radio SETI searches utilising the Green Bank Telescope over many years have produced a vast database of observations. With the large volume of this data, there still exists potential for the discovery of interesting SETI candidates—as well as non-SETI related anomalies—through re-analysis with newly developed detection methods. However, radio frequency interference is prevalent within this data, and the absence of a known reference signal makes extracting potential signals challenging. To confront these issues, we explore the application of machine learning methods designed to enhance signal detection capabilities.

Specifically, the methods explored within this work utilise a deep autoencoder trained on observational data and injected signals. By examining the latent space of the autoencoder, we explore two approaches for anomaly detection. The first employs a simple reconstruction loss method, identifying sections of the dataset with the highest reconstruction loss as anomalies. The second approach leverages the “on-off” observation pattern of the Green Bank Telescope, wherein a primary target system A is observed alternately with nearby systems B, C, or D, producing a sequence of observations in the order ABACAD. Anomalous data segments are identified if observations of system A occupy a distinct region of the latent space compared to observations of systems B, C, or D, suggesting unique signals present only during observations of the primary target.

These methods are evaluated by injecting previously unseen anomalous classes of broadband complex signals in a proof-of-concept test.

Speaker: Mr Kai Mulcock (Imperial College London)

196 Technosignature Science Programs with the Allen Telescope Array

The Allen Telescope Array (ATA) at Hat Creek Radio Observatory (HCRO) is a 42-antenna array located in Hat Creek, California. Currently, observations at the ATA are being carried out with a 28-feed beamformer and correlator for projects in multiple branches of radio astronomy, including pulsar science, fast radio bursts (FRBs) and search for extraterrestrial intelligence (SETI) surveys. Here, I will summarize recent and current technosignature projects with the ATA such as the Research Consortium of Nearby Stars (RECONS) survey, the SN 2023ixf SETI Ellipsoid monitoring, and the Anti-Solar Point (ASP) survey.

Enabling early science with Rubin LSST in 2025

Organisers: Graham Smith; co organisers: Steve Ardern, Astha, Michelle Collins, Thomas Cornish, Suhail Dhawan, Dimple, Paul Giles, Chris Lintott, Bob Mann, Garreth Martin, Steph Merritt, Mahdieh Navabi, Clara Pennock, Ana Sainz de Murieta, Jason Sanders, Matthew Temple, Roy Williams, Jacco van Loon

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) will be a major pillar of the UK astronomy programme for the next two decades. Its unprecedented combination of spatial, spectral and temporal coverage enable it to probe a broad range of astrophysical phenomena, across all areas of astronomy, from near-Earth asteroids to distant quasars, the dark energy believed to drive the Universe’s accelerating expansion, and much more.

NAM2025 coincides with a major milestone of broad impact across the UK and international communities: the first release of on-sky Rubin data to data rights holders. These data have already been obtained during observations with the commissioning camera in late 2024. Science Verification observations with LSSTCam are also expected to be well underway in summer 2025.

In addition to the parallel session there is also a lunchtime session. We aim to encourage and enable the widest possible participation and engagement with the early data, with a particular focus on early career researchers.

We aim for a balance between five themes, across these five sessions:
o Introduction: Rubin/LSST, LSST:UK, and the international Science Collaborations
o Early career science: plans for early and future science with the Rubin data
o Tutorials and examples: how to access, filter, and manipulate Rubin data
o Community insights: technical and scientific preparations by LSST:UK researchers
o Engagement: an introduction to the LSST:UK engagement programme

In addition to talks from across the community, the sessions will include training, Q+A for early career researchers, a hack session, and a facilitated discussion.

Timetable_#62.csv

14:15 Poster Flash Presentations

197 The LSST-NIR Fusion Pipeline: Advancing Multiwavelength Astronomy with Rubin LSST and VISTA

The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) is set to revolutionize astronomical research by providing unprecedented optical data. However, integrating near-infrared observations is key to unlocking the full potential of LSST, particularly for studying dusty environments and older stellar populations. The LSST-IR pipeline has been developed to combine LSST’s optical data with near-infrared observations from VISTA surveys, which extensively cover the southern hemisphere with various depth surveys, including VHS, VIKING, SHARKS, VIDEO, VEILS, KEDFS, and more. VISTA data effectively bridges the gap between IR datasets like Euclid (YJH bands) and Spitzer/WISE ($> 3.6μm$), providing essential K-band coverage for comprehensive studies.

LSST’s flexible science pipelines, designed for multi-instrument use, can be extended to other telescopes with custom obs packages. The obs-vista package and LSST-IR pipeline have already been successfully tested with Hyper Suprime-Cam (HSC) data, producing pixel-matched images and multi-band catalogues. The pipeline is now ready to run on LSST’s commissioning data, supporting a broad range of astronomy science projects.

This presentation will emphasize the significance of multiwavelength analysis using LSST-IR, the role of K-band and VISTA surveys, and the pipeline’s readiness for LSST commissioning data. The development enables various science projects, underscoring the pipeline’s versatility and its future impact on astronomical research. We also aim to engage early career researchers in accessing and utilizing these datasets, providing practical insights into working with combined optical and near-infrared data.

Speaker: Elham Saremi (University of Southampton)

198 The LSST AGN Science Collaboration and Its Early Science Plans

The LSST Active Galactic Nuclei (AGN) Science Collaboration (SC), currently composed of 230 members spanning the globe (with about 18 UK members), aims to lead many of the large-scale LSST investigations of growing supermassive black holes in AGNs. I will briefly summarize the membership and organization of the AGN SC. I will then highlight its recent and ongoing activities, including gathering and analyzing preparatory data sets (e.g., in the Deep-Drilling Fields) to allow strong early science, contributing to survey cadence optimization, forecasting science results with simulations, serving on key working groups, and performing outreach to the scientific community and general public. I will emphasize the AGN SC's early science plans and describe how interested members of the UK, European, and worldwide astronomical community can become involved.

Speaker: William Brandt (Penn State University)

Brandt-NAM-LSST-01.pdf

199 Dark matter science with Rubin LSST: weak lensing and stellar streams

The fundamental nature of dark matter so far eludes direct detection experiments, but it has left its imprint in the cosmic large- and small-scale structure. Extracting this information requires accurate modelling of structure formation for different dark matter theories (e.g., the axion), careful handling of astrophysical uncertainties and consistent observations in independent cosmological probes. I will present a novel dark matter science programme for Rubin LSST combining information from galaxy weak lensing and Milky Way stellar streams. I will present forecasts for the sensitivity of LSST year 1 cosmic shear to axion dark matter, for the first time accounting for non-linear axion structure formation and its interplay with astrophysical feedback, demonstrating how to disentangle between axion and feedback effects to the S_8 cosmological parameter discrepancy. I will further present a new deep learning method to detect the lowest-mass sub-halos to-date by their interaction with stellar streams, demonstrating up to 100 x stronger constraints on halo properties than existing approaches. By combining information from larger- and smaller-scale probes, I will argue that compelling dark matter models like the GUT-scale axion can be systematically tested for the first time.

Speaker: Keir Rogers (Imperial College London)

200 Galaxy-Halo Connection Across Cosmic Time: Preparing for LSST with Deep Survey Fields

I will present recent results on the relationship between galaxy evolution and dark matter halos using deep extragalactic surveys. I use LSST-quality optical data from HSC and VOICE, and Euclid-quality near-infrared data from VIDEO and UltraVISTA, to measure galaxy clustering in the COSMOS, XMM-LSS, and ECDFS fields.
Together, these fields cover an area of ~10 square degrees, which is five times larger than previous deep-field clustering studies. This enables us to probe the clustering of the most massive galaxies across cosmic time, not previously achieved at this depth and scale. The use of multiple independent fields helps to overcome cosmic variance, and the large area allows better sampling of the clustering between halos.
By measuring the two-point correlation function up to redshift z=4, I use halo occupation distribution (HOD) modelling to derive key parameters such as the satellite fraction, galaxy bias, and the stellar mass–halo mass relation. These reveal how galaxies occupy halos of different masses and how this evolves with cosmic time.
My analysis provides insights into the role of the environment in shaping galaxy evolution and the connection between galaxy properties and dark matter halo properties. This work demonstrates the power of wide, deep, multi-band surveys in studying galaxy environments and large-scale structure. It also serves as a prototype for upcoming clustering studies with LSST and Euclid, showcasing how early data can be used to constrain the galaxy–halo connection and providing a framework for future, larger-scale analyses with LSST.

Speaker: Natalia Stylianou (University of Oxford)

201 Enhance LSST Cosmological Cosntraints Using Data-Augmented Redshift Calibration and Variational-AutoEncoder Marginalisation

The exceptional statistical power and imaging depth of LSST will enable unprecedented constraints on the cosmological model, as well as the nature of dark matter and dark energy. However, accurately estimating ensemble redshift distributions and efficiently marginalising over their uncertainties remain major challenges. In this talk, I present a novel approach that leverages Self-Organising Maps (SOMs) to project the high-dimensional galaxy colour space into a two-dimensional representation. This allows us to identify regions of colour space poorly sampled by spectroscopy, which we then augment using synthetic galaxy catalogues to construct representative training datasets for photometric redshift estimation. Our method achieves sub-percent accuracy in the mean redshift distribution for both one-year and ten-year observations of Rubin and models realistic variations due to systematic effects. These results offer valuable insights for photometric redshift calibration using LSST early science data.

Using these simulated redshift distributions, we demonstrate that conventional parametrisations significantly underestimate statistical uncertainties—by up to an order of magnitude for galaxy clustering. To address this, we employ a Variational Autoencoder (VAE) to compress redshift distribution realisations into a Gaussianised latent space, enabling more efficient and accurate marginalisation. Cosmological forecasts show that weak lensing constraints remain robust regardless of marginalisation technique. However, when combined with large-scale structure datasets, our VAE-based method recovers a 20% downgrade in the Figure-of-Merit, correcting the overestimation from standard approaches. This highlights the necessity and effectiveness of our framework, which will be integrated into the LSST-DESC inference pipeline for collaboration-wide application in future precision cosmology analyses.

202 The Effects of Template Generation in Year 1 of LSST

The Vera C. Rubin Observatory will commence the 10 year Legacy Survey of Space and Time (LSST) this year in 2025. Within 60 seconds of the shutter closing LSST will issue rapid, public alerts of transient sources found in each visit. To detect these sources templates of the static sky are required to conduct difference imaging. However, in Year 1 of LSST the sky is visited for the first time and templates must be generated as the survey progresses, which will limit the visits able to produce alerts. We have assessed the effects of template generation using the Metric Analysis Framework and the latest survey simulation (one_snap_v4.0_10yrs). We focus on discovery metrics for Solar System Objects (SSOs) and find that the ability of LSST to discover SSOs in real-time is greatly reduced when template generation is required. Sky regions that are scheduled to receive fewer visits, such as the North Ecliptic Spur (NES), or filters that are less frequently sampled (e.g. u and g), show the greatest loss of alerts. Relative to the baseline survey strategy, up to 79% of Main-Belt asteroids in the NES will not receive real-time discovery alerts. These alerts are not lost per se as all visits will be reprocessed in subsequent data releases; but the opportunities for rapid follow-up observations will be greatly reduced. This is particularly relevant for discovery of potentially hazardous asteroids and interstellar objects, but the lack of real-time alerts is sure to have an impact on many other LSST science goals.

203 Forecasting Cosmological Constraints from LSST Strong Lenses: A Multi-Probe Hierarchical Approach

I this talk I will present a forecast for the cosmological constraints expected from all the galaxy-scale strong gravitational lenses identified in the Rubin Observatory (LSST). In particular, the constraints are provided by the following SL sub-probes: lensed quasars, lensed supernovae, double source-plane lenses (DSPL), and galaxy-galaxy lens Einstein Rings, both with and without follow-up data. We plan to emulate a fully self-consistent joint hierarchical inference of cosmological parameters given a mock lens sample, and investigate the information content provided by each sub-probe. I will also talk about the challenge of the follow-up observations and coordinations with other survey facilities.

A multi-scale and multi-tracer view of the cosmic web

Organisers: Rita Tojeiro, Alyssa Drake, Meghan Gray, Andrew Pontzen, Tianyi Yang

The cosmic web is the characterisation of the matter distribution in the Universe into distinct environments – nodes, filaments, sheets, and voids – that are shaped by the anisotropic nature of gravitational collapse. Each distinct cosmic web environment has been shown to play an important role in the evolution of dark matter halos and galaxies via a variety of complex, multi-scale physical processes. The collective impact of these environments on galaxy and halo transformation is fundamental and diverse: for example, depending on scale, cosmic web environments can sustain galaxy and halo growth, but also inhibit it through stripping or tidal effects.

Our ability to study this impact is driven by rapid advancement of larger, denser, and deeper spectroscopic surveys alongside new generations of cosmological hydrodynamical simulations. We invite talks that consider the evolving anisotropic environment of galaxies and halos from the scales of the circumgalactic medium to that of massive clusters, and that trace the cosmic web via gas, galaxies, dark matter, or galaxy-CMB crosscorrelations. The goal of this session is to bridge research across scales and tracers, in simulations and in observations, such that the UK community can progress on questions such as:

o How do cosmic web environments influence galaxy and halo evolution across scales?
o How can cosmic web environments traced through different methods be compared?
o What links the anisotropic circumgalactic medium to larger-scale cosmic web structures?
o How do galaxies and halos transform as they traverse cosmic web environments?
o How does the cosmic web drive transformations over cosmic time?

204 The Role of Filaments in Galaxy Evolution

Cosmic filaments—shaped by 13.7 billion years of structure growth—play a fundamental role in galaxy evolution. At least half of all galaxies reside in filaments, the bridges of matter that channel them into clusters while exposing them to diverse environments. These large-scale structures regulate gas flows, linking galaxies to the intergalactic medium and influence their ability to accrete fresh gas or undergo environmental quenching. As a result, key galaxy properties such as colour, star formation rate, morphology, and spin strongly correlate with their position in the web.

What drives these correlations? Are they shaped by the interplay of large-scale structure formation, local density physics, fine-scale gas processes, or internal mechanisms? Despite the observed global trends, the underlying physical explanations remain an active area of research and debate.

For one, it is notoriously difficult to map such a complicated structure, given the incomplete, noisy, and biased nature of observational data. In addition, the processes at play are likely subtle and cumulative rather than dominated by a single factor.

As we enter an era of large-scale, multi-wavelength surveys and high-resolution simulations, we have an unprecedented opportunity to synthesize observations, simulations and theory into a global framework.

I will provide a high-level review of our current understanding of how galaxies and the cosmic web co-evolve, focusing on the role of filaments and clusters in shaping galaxy transformation, as well as how we map the multi-scale structure of the cosmic web.

205 A 15 Mpc rotating galaxy filament

Galaxies do not form in isolation, they grow within the large scale filaments, which affect their formation and evolution. However, the extent to which the cosmic filaments shape galaxies has not been yet understood. Particularly, how the proximity to filaments affects the orientation of a galaxy with respect to the filament and how it can provide important insights into its intrinsic properties. In this talk, I will present the results from the state-of-art radio survey MIGHTEE-HI conducted with the MeerKAT radio telescope (an SKA pathfinder) and show how observations of neutral hydrogen in galaxies are instrumental to enhance our knowledge of galaxies growth. Specifically, I will focus on a recent discovery of a ~15 Mpc cosmic filament in which the galaxies within show strong alignment, as well as hints of rotation around the spine, making it of the largest rotating structures seen thus far.

206 Evidence that pre-processing in filaments drives the anisotropic quenching of satellite galaxies in massive clusters

We use a sample of 11 $z\approx0.2-0.5$ galaxy clusters from the Cluster Lensing And Supernovae survey with Hubble (CLASH) to analyse the angular dependence of satellite galaxy colour $(B-R)$ and passive galaxy fraction ($f_{\text{pass.}}$) with respect to the major axis of the brightest cluster galaxy (BCG). This phenomenon has been dubbed as \say{anisotropic quenching} describes how satellite galaxies along the major axis BCGs are more likely to be quenched than those along the minor axis. We find a highly significant anisotropic quenching signal for satellites, with a peak in $(B-R)$ and $f_{\text{pass.}}$ along the major axis. We are the first to measure anisotropic quenching out to cluster-centric radii of $3R_{200}$ ($R_{200\text{, med.}} \approx 933$ \si{\kilo\parsec}). We find that the signal is significant out to at least $2.5R_{200}$, and the amplitude of the signal peaks at $\approx1.25R_{200}$. This is the first time a radial peak of the anisotropic quenching signal has been measured directly. We suggest that this peak could be caused by a build-up of backsplash galaxies at this radius. Finally, we find that $f_{\text{pass.}}$ is significantly higher along the major axis for fixed values of local surface density. The density drops less rapidly along the major axis and so satellites spend more time being pre-processed here compared to the minor axis. We therefore conclude that pre-processing in large-scale structure, and not active galactic nuclei (AGN) outflows, is the cause of the anisotropic quenching signal in massive clusters, however this may not be the cause in lower mass halos.

Speaker: Harry Stephenson (Lancaster University)

207 Exploring how galaxy colour depends on local environment measures and geometric environment

The relative abundance of the red and blue galaxy populations has been found to vary with stellar mass and environment. We explored the effect of environment considering different types of measurements using a sample of 50,000 galaxies with $0.05 < z < 0.18$. We studied the dependence of the fraction of red galaxies on different measures of the local environment as well as the large-scale `geometric’ environment defined by density gradients in the surrounding cosmic web. By comparing the different environmental densities, no density measurement fully explains the observed environmental red fraction variation, suggesting the different measures of environmental density contain different information. We tested whether the local environmental measures, when combined together, can explain all the observed environmental red fraction variation. The geometric environment has a small residual effect, and this effect is larger for voids than any other type of geometric environment. This could provide a test of the physics applied to cosmological-scale galaxy evolution simulations as it combines large-scale effects with local environmental impact.

208 The CAVITY project: tracing the evolution of galaxies in cosmic voids through IFS

The impact of the void environment on galaxy evolution is a subject of growing interest, yet many questions remain unanswered. The Calar Alto Void Integral Field Treasury surveY (CAVITY) project aims to address this issue from a novel perspective: using both spectroscopic and spatially resolved data through optical integral field spectroscopy (IFS).

We analyze the CAVITY data cubes with the non parametric full spectral fitting algorithm STARLIGHT to obtain their stellar population properties, and measure their emission lines to get their nebular content. We obtain maps of stellar mass, stellar ages, star formation rate (SFR), and specific SFR (sSFR), based on both stellar star formation histories (SFHs) and Hα luminosities. To assess the impact of large-scale structure, we compare our findings with a control sample of galaxies in filaments and walls, matched in stellar mass and morphology, using data from CALIFA, which shares the same observational setup and analysis methods.

Our results indicate that void galaxies evolve more slowly than their counterparts in denser environments, particularly those with intermediate morphologies (e.g., Sa galaxies). Additionally, we find that the outskirts of late-type galaxies are more strongly influenced by the void environment. These findings demonstrate the potential of the CAVITY project to advance our understanding of how large-scale structure shapes galaxy evolution.

15:37 Poster annoucements

Blue sky to night sky: development of astronomical instrumentation

Organisers: Carolyn Atkins, Cyril Bourgenot, David Lee, Matthias Tecza

This session invites contributions that present innovative concepts, emerging technologies, and new designs driving the future of astronomical instrumentation. From conceptual blueprints to unique prototypes and advanced systems, speakers will have the opportunity to present their latest ideas and developments, including those in early development, and to discuss the challenges and opportunities associated with their realization.

The session aims to foster interdisciplinary collaboration and spark creative dialogue, covering a broad range of topics such as additive manufacturing, multi-object spectrographs, integral field units, adaptive optics, detector advancements, and novel telescope designs. Whether addressing ground or space-based instrumentation, we welcome fresh perspectives and ideas on instrumentation development that will define tomorrow’s observational astronomy.

209 The Wide-field Spectroscopic Telescope: developments in fibre positioning technology

A new generation of observatories dedicated to multi-object spectroscopy (MOS) are required to follow up on current and future all-sky imaging surveys. These facilities demand a step change in multiplex and efficiency compared to contemporary instrumentation, bringing profound engineering challenges. This paper will explore current technology development associated with the Wide-field Spectroscopic Telescope (WST), a proposed 12m telescope with more than 20,000 fibres covering the visible and near-infrared wavelengths. Focusing on front-end hardware architecture, it will first describe the state-of-the-art from MOS instruments like MOONS, 4MOST and DESI, the engineering consequences of the required increase in multiplex and efficiency, then will discuss the technology development programme currently underway at the UK Astronomy Technology Centre at the Royal Observatory Edinburgh to develop novel fibre positioner mechanisms, fibre management systems, control electronics and software to address the WST requirements.

210 Calibration, characterisation and contrast measurements with a prototype twisted image slicer for ELT-PCS R&D.

Image slicers are becoming an increasingly dominant integral field unit (IFU) technology and will be a key component in a number of upcoming instruments for 20-40m class telescopes. They offer efficient use of the detector space, high throughput and simpler routes to coupling with high dispersion spectroscopy. For ESO’s upcoming Planetary Camera and Spectrograph (ELT-PCS) instrument, which aims to detect rocky Earth-like exoplanets at extreme contrast ratios, image slicers are therefore a highly appealing technology for its integral field spectrograph (IFS).
A prototype “twisted” image slicer, developed at Oxford as part of R&D for ELT-PCS and manufactured by Canon Inc., eliminates the need for anamorphic optics by generating spatially and spectrally Nyquist-sampled pseudo-slit images at the detector while retaining square spaxels on-sky. The lack of anamorphic optics simplifies optical design and reduces aberrations in the system, providing an advantage for reaching high contrast. This talk will provide an overview of the twisted slicer development and integration within the ELT-PCS integral field spectrograph testbench at Oxford. We will discuss the various techniques for spatial and spectral calibration implemented to convert the 2D detector images to 3D data cubes. Finally, data cubes and contrast measurements from the testbench will be presented to analyse the performance of the twisted image slicer in an IFS for direct imaging, and future plans for integration of the IFS at ESO Garching behind the GHOST XAO testbench will be outlined.

Speaker: Ryan Griffiths (University of Oxford)

211 Two Photon Polmerisation for astronomy

Two-Photon Polymerisation is a form of additive manufacturing (3D printing) allowing the creation of structures on nano to macro scales. Its versatility means it has already found its way into a number of fields from life sciences to integrated photonics and microfluidics. Of particular interest to astronomy is the ability to “print” micro-optics.
Here I show some of the amazing structures that can be created with Two-Photon Polmerisation and then delve into the work developing Two Photon Polymerised devices for astronomy. I detail the work developing microlenses to increase coupling into fiber fed instruments before moving onto micro-spectrographs designed as low-resolution dispersers for cryogenic instruments. I then discuss where I think some of the future applications lie.

212 A lobster eye telescope for the Jovian system

We present an X-ray imager concept for the Jovian system. With the advancement of light-weight, novel lobster eye X-ray instrumentation, it is now possible to send an X-ray imaging telescope to the outer solar system, building on the heritage gained at the University of Leicester for such instrumentation (MIXS on BepiColombo, LEIA, WXT on EP, MXT on SVOM and SXI on SMILE). The Jovian system is host to a large range of processes generating X-rays, including energetic particle precipitation onto the surfaces of the moons, charge exchange in the Io plasma torus, the planetary X-ray aurorae, and inverse-Compton scattering in the radiation belts. Measuring these emissions can provide insights into Jupiter’s magnetosphere and sources, sinks and processes in particle populations. We discuss methods of radiation hardening to mitigate the unique challenges posed by Jovian system and its high radiation background. We present the concept of an X-ray imager and discuss the processes of X-ray production, science gains and the technology developments still required for such an instrument.

Speaker: Ms Natasha Carr (University of Leicester)

213 An Affordable and Easily Programmable Homodyne Readout System for Readout and Characterisation of Prototype MKIDs (Microwave Kinetic Inductance Detectors) for UVOIR Astronomy and Astrophysics

Many modern astronomy instruments are now using superconducting detector technologies due to the advantageous properties of low-temperature superconducting materials. The very small superconducting bandgaps of some metals allows photon counting and energy resolving capabilities in wavebands spanning near/mid-infrared to X-ray, and time-integration measurements in the far-infrared, sub-millimetre, and CMB wavebands. The complexity of most readout electronics systems for large arrays of superconducting detectors often requires powerful and expensive processors such as FPGAs, CPUs, and/or GPUs. However, during prototyping stages of detector development, it is often sufficient to readout single pixels/channels at any one time.
In this paper we present an RF homodyne readout system based on the Red Pitaya educational FPGA board. The system is designed to readout prototype MKID (microwave kinetic inductance detector) pixels designed for UVOIR astronomy and astrophysics. The very affordable and easily programmable system was built with off-the-shelf-components including an IQ mixer and bench-top programmable LO, and is programmed with python.
Full characterisation of the system components will be presented, and results will be shown for the system during operation as a readout for prototype optical/near-IR MKIDs. The system can operate in frequency domain ‘sweep mode’, to search or trace the resonance of an MKID resonator in amplitude, phase, and IQ data formats. The system can easily be switched to time domain ‘pulse mode’, which can be used to monitor a single pixel for photon events. A summary of the system design and performance will be presented, along with some science data recorded with the system.

Speaker: Dr Colm Bracken (Maynooth University)

214 SPT-SLIM: First light and spectral calibration

The South Pole Telescope Shirokoff Line Intensity Mapper (SPT-SLIM) experiment is a pathfinder for demonstrating the use of multipixel on-chip spectrometers for millimeter (mm) Line Intensity Mapping (LIM). SPT-SLIM targets the CO rotational transitions from galaxies with redshifts ranging $z\sim0.5$--$3$ to map the large-scale structure of the Universe through hyperspectral imaging. SPT-SLIM achieved first light during the austral summer 2024-2025 observing season, leveraging superconducting filterbanks to provide $R\sim100$ imaging spectroscopy in the 120--180 GHz atmospheric window. Each of the five operational spectrometer devices couples light from an on-sky antenna to a series of 130 spectral filters, each terminated in a lumped-element kinetic inductance detector (KID).
We present early observations demonstrating the instrument and a comprehensive set of spectral calibration measurements of the SLIM submodules. Leveraging laboratory measurements with Fourier transform spectrometers, we have measured the spectral response and mm performance of the spectrometer pixels.

Star formation across environments: From individual molecular clouds to entire galaxies

Organisers: Eva Duran Camacho, Rebecca Houghton, Elizabeth Watkins; co organisers: Helena Faustino Vieira, Rowan Smith, Thomas Williams

Star formation (SF) is a fundamental process in the Universe, driving processes from the chemical and physical evolution of galaxies down to the initial conditions for planet formation. Local star forming processes, such as stellar feedback, and the larger galactic environment self-interact, altering star-forming conditions within individual molecular clouds and within galaxies globally. However, we still do not have a complete picture of SF across different scales and environments, from both observational and theoretical perspectives.

During this session, we will aim to:
o Link SF studies across different physical scales and environments (i.e. spiral arms, inter arms, galactic centres, and outer galactic regions).
o Improve cross-disciplinary discussions and encourage collaboration between observers and theorists.

The session will be divided into two blocks. The first block will explore resolved SF within individual molecular clouds and their connections to their galactic environment. The second block will provide insights on how galaxy evolution and galaxy-scale structures impact molecular cloud properties and SF within. Each block will consist of a 75-minute series of talks (1 review and ~4-5 contributed), followed by a 15-minute discussion on open questions in the field and how to address them, from both an observational and theoretical standpoint.

With facilities such as JCMT, ALMA, and JWST providing a wealth of new information both in the Milky Way and in nearby galaxies, this session will share the latest results across the star formation community and facilitate discussions between both simulators and observers working across different scales and environments.

215 Protostellar jets and their effects on the surrounding ISM

Protostellar jets play a pivotal role in injecting matter and momentum into their environment, influencing regions several parsecs in size. This feedback mechanism significantly impacts the dynamics, morphology, and fragmentation of molecular clouds, which in turn, affects the formation of subsequent protostars. Understanding how jets regulate accretion processes and filamentary structures is critical for accurately modelling star formation. In this submission we present a novel subgrid model within the widely-used hydrodynamic simulation code, AREPO, to simulate protostellar jet feedback. Our approach injects mass and momentum into conical volumes near the sink particles, with adaptive mesh refinement ensuring numerical consistency. This methodology enables an investigation of the interplay between jet-driven feedback and filamentary evolution. Areas of particular interest include the alignment between the jets and the filaments; the impact on the lifetime of the filaments by the jets; and measuring the correlation between the abundance and strength of the jets with the star formation efficiency. Ultimately, this work aims to enhance the predictive power of simulations, bridging the gap between theoretical models and observations.

216 Bridging the scales from global galactic dynamics to local star formation

Understanding the interplay between galactic dynamics, star formation, and stellar feedback is crucial for constructing a comprehensive model of star formation. To explore how the large-scale environment affects local star formation, we simulate an isolated star-forming galaxy and zoom into different regions to characterise how star formation varies in relation to bulk properties.
The galaxy is modelled with the 3D magnetohydrodynamic moving-mesh code AREPO and includes stellar feedback, radiative transfer, non-equilibrium chemistry, a live potential and magnetic fields. Star formation is simulated with a sub-grid module which forms ‘star particles’ which have photoionising and supernova feedback mechanisms.
We improve upon existing zoom-in methods in several ways: by incrementally increasing the resolution of nested regions centred on a point of interest to minimise boundary artifacts, by using a flow-tracing method to track region boundaries for self-consistent evolution within a certain duration, and by assessing the validity of our zoom-in simulations by comparing them to the original large-scale simulation. We apply this zoom-in method to regions in the spiral arms, the inter-arms, the central molecular zone, and the outer galaxy with the aim of revealing systematic variations in star formation properties across these different environments, and linking them to the empirical star formation laws.
This framework provides a more self-consistent method for multi-scale galaxy simulations, offering a better characterisation of the role of the galactic environment in star formation.

217 Resolving spiral arms, clumps and bulges in Cosmic Noon Galaxies with JWST and ALMA

Galaxies experienced a critical phase of rapid evolution 8–10 billion years ago (Cosmic Noon), shaping the morphological types seen in the local Universe, with characteristic features like bulges and spirals. However, direct imaging of these substructures in formation was not possible before JWST. I will present a series of works where we exploit JWST/NIRCam and ALMA images to fully 'deconstruct' Cosmic Noon star-forming galaxies at redshift (z)~1.5 into subcomponents like bulges, disks, star-forming clumps, and spiral arms. The aim is to understand how typical main-sequence galaxies undergo rapid morphological transformations to establish the Hubble sequence. We find that the buildup of the central bulge leads to a lowering of the star-formation efficiency in the host galaxy. However, this is due to the gas being concentrated at the centre, which ends up lowering the efficiency with which gas is converted to stars. Meanwhile, in the disk, we find that star-formation is mainly concentrated in star-forming clumps and spiral arms, both of which are expected to be massive enough to simultaneously funnel gas to the centre. Star-formation in these structures is found to occur over a hierarchy of spatial scales, with mass distributions closely resembling those of star-forming regions in the local Universe. Finally, we study the spiral structures and find a fraction of them exhibiting density-wave-like characteristics. This suggests that the spirals in z>1 galaxies are not just signs of tidal interactions or stochastic star-formation in a differentially rotating disk. In fact, propagating density waves are already in place at z~1.5.

218 How star formation-driven galaxy-scale outflows regulate star formation

Star formation driven outflows play an important role regulating the gas supply of galaxies, thus regulating the star formation. However, we still need a consensus on the details of this feedback process, particularly in starbursting environments. I will present results from the DUVET sample of local starbursting galaxies observed using the IFU KCWI/Keck. We measure ionised gas outflows in 10 face-on galaxies with ~1000 individual measurements at 500pc resolution. Using our observations (1) we can discriminate between widely used models of the outflow launching mechanism. (2) We derive much-needed scaling relations for the relationship between star formation and outflow properties across a range of star-forming environments and compare these to simulations. (3) We compare to observations from NOEMA, and connect the outflows with location in the resolved Kennicutt-Schmidt relation to find that starburst regions remove more gas via the outflow than they convert into stars. This directly measures how outflows regulate star formation and may contribute to quenching. DUVET's resolved outflow observations provide a new perspective to make ground-breaking constraints on how stellar feedback regulates star formation.

219 Environmental quenching of star formation: the case of the Fornax cluster

Galactic environment is thought to be one of the key factors in driving the cosmic quenching of star formation in galaxies. The Fornax cluster is a nearby intermediate-mass cluster that is more representative of the clusters found in the Universe compared to other nearby clusters such as Virgo and Coma. Recent deep optical and radio observations (with VST and MeerKAT) revealed several interesting Fornax galaxies with on-going gravitational and hydrodynamical interactions affecting their neutral-gas content and optical morphology, likely conducive to quenching. To further gain insight on the physical mechanisms behind such phenomena, we derive the star-formation history of Fornax galaxies with a spectrophotometric approach to both MUSE integral-field spectroscopic and S-PLUS imagining data. At the same time we also explore Fornax-like clusters in the TNG-50 simulations to derive the neutral-gas predicted distribution both across the whole cluster and around individual galaxies, following this also in time. This gives us a view of both on-going gravitational and hydrodynamical interactions in the Fornax cluster galaxies as well as a gauge on the past impact that these had in driving their star-formation histories, which we can compare to model predictions.

15:30 Poster Flash Presentations / Open discussion session

15:45 Coffee Break

15:45 Moon Palace open to conference attendees

17:00 Coach to Newcastle - departure

17:45 Coach to Newcastle - arrival

18:15 NAM 2025 dinner - drinks reception

19:00 NAM 2025 dinner & awards

22:30 Coach back to Durham

Wednesday 9 July

08:00 Registration and set up

The Extremely Large Telescope: Science and Instrumentation

Organisers: Kathryn Hartley, Aurelie Magniez, Deborah Malone, Kieran O'Brien

The European Extremely Large Telescope (ELT) is currently under construction by a consortium of leading research institutes across Europe, including notable contributions from institutions in the UK. This groundbreaking telescope is poised to usher in a new era of high-resolution imaging, facilitated by its advanced adaptive optics systems and highly sensitive instruments.

This session will offer a platform for project participants to showcase their contributions to the construction of the telescope and its scientific instruments. Additionally, it will provide an overview of the anticipated scientific missions and the transformative impact these missions are expected to have on our understanding of the universe. Attendees will gain insights into the innovative technologies employed, the collaborative efforts driving the project, and the future research opportunities enabled by the ELT.

Timetable_#67.csv

09:00 Prep time

220 HARMONI on the Extremely Large Telescope

HARMONI is the first-light near-infrared Integral Field Spectrograph (IFS) planned for the European Extremely Large Telescope (ELT).
I will present the planned capabilities of this uniquely powerful instrument, which will offer a near ten-fold improvement in both the angular and spectral resolution currently provided by the James Webb Space Telescope (JWST) at near-infrared wavelengths. I will also update the community on current progress in the design/build of this, the first key UK-led instrument for the ELT. Finally, I will discuss some example science cases to highlight the dramatic advances that should be enabled by HARMONI given the near diffraction-limited resolution anticipated from the ELT Multi Conjugate Adaptive Optics (MCAO) system, MORFEO.

Speaker: Prof. James S. Dunlop (University of Edinburgh)

221 The METIS instrument for the ELT

We will briefly describe the performance parameters of the METIS thermal infrared instrument and its current build status, concentrating on the L- and M-band integral field, coronagraphic high resolution spectrometer (the LMS), which comprises the UK's contribution to the METIS project.

Speaker: ALISTAIR GLASSE (UK Astronomy Technology Centre)

222 MICADO: overview and status of the ELT first light imager and spectrograph

MICADO will be the first instrument available at the ELT. Using adaptive optics (its own SCAO system as well as the MORFEO system being built by INAF), it will enable unprecedented resolution at near-infrared wavelengths, providing diffraction limited imaging, astrometry, high contrast imaging, and slit spectroscopy. I will describe the MICADO project, indicate a few science cases that exploit its various observing modes, and present its current manufacturing status.

Speaker: Ric Davies (MPE)

223 Observing young stars with METIS

The field of star and planet formation has enormously profited from the availability of high spatial resolution and infrared capabilities, although those so far do not always come together. The METIS instrument will provide high sensitivity, high spatial resolution, and high spectral resolution, which all combined are key to unveil the inner regions of protoplanetary discs, including the star-disc connection, and to probe faint and embedded systems. I will present possible observation scenarios for young stars and their innermost regions, including mapping the inner discs, detecting accretion and accretion modes, and studying the time variations at scales relevant for the inner planet regions.

Speaker: Aurora Sicilia-Aguilar (University of Dundee)

224 Airglow Characterisation for ELT-era Observations

Light emission from the atmosphere, known as airglow, is imprinted on all ground-based observations. Airglow is particularly strong and dense in near-infrared spectra, forming a forest of emission lines with fluctuating intensities. To ensure observations taken with ELT instruments are used to their full potential, an ELT working-group on sky-subtraction has been established by ESO in collaboration with instrument consortia so that airglow can be removed from science data to the required sub-percent accuracy.

The working group’s current focus is on the characterisation of airglow lines, as many molecular transitions are uncatalogued and their temporal and spatial variations are poorly constrained. We present the latest progress of this effort after 26h of VLT observations on CRIRES+ in the 1.2-1.8µm wavelength range. These deep and high-resolution (R ~ 100,000) observations allow us to showcase newly catalogued faint-lines that at lower resolution masquerade as a pseudo-continuum, and we discuss how they vary temporally and spatially over 10 minute and 10" scales respectively. Finally, we present the implications of this work on various ELT instruments, most notably MOSAIC, the ELT’s multi-object spectrograph.

Speaker: Jay Stephan (UK Astronomy Technology Centre)

The Future of Exoplanet Detection

Organiser: Aurelie Magniez; co organisers: Kathryn Hartley, Deborah Malone

Scientific interest in the search for exoplanets has reached a new level with the development of innovative technologies that promise to reveal undiscovered planetary systems. The current instruments, which use techniques such as radial velocity, direct imaging or transit, have enhanced our comprehension of exoplanets. However, their capabilities are constrained to observing only a limited number of planetary systems. To overcome these constraints, researchers are developing innovative technologies and methods in spectroscopy, adaptive optics, interferometry and other areas with the aim of improving performance. Consequently, innovative projects such as the PLATO space mission and the Planetary Camera Spectrograph (PCS) on the Extremely Large Telescope (ELT) are being developed to observe a wider range of exoplanets in greater detail. These instruments will facilitate the identification of smaller, Earth-like planets and provide deeper insights into their atmospheres and potential habitability.

This session will present the latest advances in exoplanet instrumentation, emphasise significant forthcoming missions, and examine how these developments will enhance our capacity to detect and characterise exoplanets, unlocking new avenues for understanding planetary systems.

09:00 Prep time

225 R&D activities at Oxford for the ELT-PCS integral field spectrograph.

In order for ESO’s Planetary Camera and Spectrograph for the ELT (ELT-PCS) to image rocky exoplanets at small angular separations around nearby stars, each component of the instrument (IFU, XAO, Coronagraph, postprocessing etc.) will need to operate at the maximum possible performance. As a result, the R&D phase of the instrument development, recently kicked off in September 2024 at ESO Garching, presents an opportunity to develop and explore new high contrast imaging techniques before the design and build phases begin. In this talk we will present both current experiments and future plans for ELT-PCS R&D activities at Oxford into integral field spectrograph (IFS) technologies. This includes early results from our modular IFS testbench system with which the performance of a novel “twisted” image slicer-based IFU and a traditional BIGRE-like lenslet IFU will be compared. We will further discuss plans to test the two IFU technologies through integration of our testbench IFS with the GHOST XAO system at ESO in the coming months. Finally, high dispersion spectroscopy (R≥100,000) across the Oxygen A-band at 765 nm has been highlighted as a likely requirement of the ELT-PCS instrument due to its status as a key biosignature, and to further isolate planet signals from speckles which contain only the stellar spectrum. We will outline plans to adapt the current testbench design to include a high-dispersion spectrograph which may be used to explore the limitations of these techniques on the testbench.

Speaker: Ryan Griffiths (University of Oxford)

226 Exoplanet Spectroscopy and Planetary System Architectures with VLTI/BIFROST

We present the exoplanet and planet formation science case for a new beam combination instrument for ESO’s VLT Interferometer, named BIFROST. This instrument is funded through the European Research Council and is due to be commissioned on Paranal in 2026 as part of the "Asgard Suite" of VLTI visitor instruments.

BIFROST will be the first VLTI instrument optimised for short wavelengths (1-1.7 micrometer) and high spectral resolution (up to R=25,000). This will allow us to measure the alignment between the stellar spin axis and the planetary orbital axis — even for wide-separation systems where this information is inaccessible with other techniques. These constraints will provide unique insights on the dynamical processes that shape system architectures.

To characterise the planets themselves, BIFROST will utilise dual-field interferometry, where the star-light suppression from adaptive optics is combined with star-light suppression from interferometry by placing the instrument fiber off-axis and adjusting the optical path delay to record at the predicted delay position of the planet. BIFROST will be able to employ this method in J and H-band, providing access to additional molecular tracers, such as the O2 absorption bands. These tracers are highly complementary to the K-band probed by GRAVITY and provide further constraints for atmospheric retrieval.

Finally, we will discuss the prospect of using BIFROST's high spectral and high angular resolution to study accretion onto young planets. Resolving the gas kinematics in circumplanetary discs would enable not only a direct mass measurement, but also inform us how planets gain their mass.

Speaker: Prof. Stefan Kraus (University of Exeter)

227 The SCALES slenslit: a novel integral field unit concept for Exoplanet characterisations built in Durham University

SCALES (Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy) is a high-contrast Integral Field Spectrograph (IFS) operating in the 2–5 micron range, designed for detailed studies of exoplanets and their atmospheres. Like other lenslet-based IFSs, it generates a short micro-spectrum for each micro-pupil formed by the lenslet array.
To enhance spectral resolution, an image slicer was integrated behind the lenslet array. This component reorganises selected micro-pupils into a pseudo-slit, effectively increasing the spectral resolution. The combined lenslet-slicer system, known as a "slenslit," enables SCALES to achieve significantly higher spectral resolution- more than an order of magnitude improvement - allowing for more precise atmospheric modelling.
This presentation provides an update on the instrument’s fabrication, with a focus on the development of the Slenslit module.

Speaker: Cyril Bourgenot (Durham University)

228 Decoding Machine Learning for Spectroscopic Atmospheric Characterisation

Recent spectral observatories stand to revolutionise our ability to study exoplanets on a larger population scale than ever before. New space-based instruments such as Ariel, alongside existing ground-based spectrographs at the ELT are set to generate vast quantities of atmospheric spectral data over the next ten years. Analysing this data requires extracting information about the planetary atmosphere from the spectra. For anything outside a small number of targets this is very computationally resource intensive, which is a large barrier to entry as we move into these larger scale planetary surveys.
The use of ML has been proven as a powerful tool in tackling this, reducing computational resources required. However, the scale of these models means this advantage comes at the cost of understanding.
We go beyond existing approaches, presenting a novel method of interpretability based on physically motivated forward modelling, bridging the gap between ML and traditional approaches.
We trained a convolutional network architecture to predict the atmospheric abundances of 5 molecules across 40,000 simulated Ariel spectra, then compare a selection of existing techniques for interpreting predictions. Based on this analysis we propose a novel application of the perturbation sensitivity technique for interpreting ML predictions.
This method has potential for use outside of Ariel data, and we believe the opportunity to share it here would help unlock barriers to entry in the use of ML for planetary spectral analysis across ground and space based observations.

Speaker: Jools Clarke (UCL)

Active Galactic Nuclei – from ISCO to CGM and from cosmic dawn to the present day

Organisers: Carolina Andonie, Vicky Fawcett, Jiachen Jiang, Amy Knight, Amy Rankine, Matthew Temple

AGN are multi-scale phenomena, with interesting physics operating from the event horizon to the circumgalactic medium. In this session, we will bring together research on different aspects of SMBH accretion physics, AGN population studies, and AGN demographics. In this session we will cover:

Accretion discs, jets and outflows in the centers of AGNs. With the recent launch of Xrism and the ongoing success of existing missions, there is a wealth of data from high-energy telescopes. We will accept presentations of observational data analysis, observation-related numerical simulations, and theoretical research for this first session. We also encourage presentations of multi-wavelength and multi-messenger observations.

Obscuration in AGNs from both dust and gas, examining the accretion and host galaxy properties of different AGN populations such as obscured AGNs, red quasars, and HotDOGs. What can these different AGN populations tell us about the SMBH-galaxy connection?

Current and future large-scale surveys such as SDSS, 4MOST, MOONS, WEAVE, DESI, LSST, Euclid and LOFAR. These facilities will produce unprecedented samples of millions of AGN. With the UK taking a leading role in many of these projects, NAM is an excellent opportunity to examine the completeness of our AGN census, and the accretion, galactic and large-scale environmental properties of AGN across luminosity, stellar masses, and cosmic time.

229 JADES census of Type 1 AGN: characterising spectral features and host galaxies of faint black holes across cosmic time

The growth of supermassive black holes and their interaction with their host galaxies still holds many unanswered questions such as the uncertainty surrounding the formation of the first supermassive black holes embedded in first galaxies. The launch of JWST was expected to shed more light on this domain by probing the low mass, low luminosity end of the active galactic nuclei (AGN) distribution - a regime missed by previous all sky surveys which were sensitive only to the brightest objects. However, the first year of results has revealed some peculiar properties of this low luminosity AGN population. Among the more notable ones being their offset compared to the local black hole mass - stellar mass relation, X-ray weakness and prevalence of absorption features in their broad lines. In this talk I will present a robust sample of Type 1 AGN from the JADES survey spanning redshifts 2 to 9. I will focus on the redshift evolution of the BH - host galaxy scaling relations and potential emission line tracers of the gas producing Balmer absorption. In particular, I will discuss how strong narrow OI8446 line emission present in many AGN with absorption features, coupled with the lack of OI7774 line implies that these lines are produced by Lyman beta fluorescense at BLR-like densities, while their narrow widths suggest that they may be tracing emission from the gas producing the Balmer absorption.

Speaker: Ignas Juodžbalis (University of Cambridge)

230 A distinct type of intrinsically narrow-line AGN in dense gas cocoons at high redshift

The James Webb Space Telescope has revealed a large number of galaxies with broad hydrogen/helium lines and bright infrared continua in increasing numbers at $z>4$. Unlike most known Active Galactic Nuclei (AGN), these systems, dubbed "Little Red Dots", lack characteristic X-ray or radio emission, as well as optical variability. Together with frequent Balmer absorption features in them, the evidence suggests that they have large column densities of neutral absorbing gas with a high covering fraction. In this work, for a sample of high-quality spectra we show that line broadening is dominated by electron scattering in dense ionized gas with only narrow line cores being explained by Doppler motion. As the electon-scattered lines yield system sizes less than tens of light days, their luminosities can only be explained by the SMBH accretion. Therefore, these high-redshift SMBHs have low masses ($10^5-10^7\,M_{\odot}$) and accrete close to the Eddington limit. They are embedded into Compton-thick gas, which likely absorbs some of the low-energy X-rays and suppresses the radio emission. This gas is likely accreted in a quasi-spherical structure that has not yet flattened into a torus-like system. Together, this evidence suggests that we are seeing an early stage of SMBH growth that has a unique set of observed characteristics.

231 A striking signature of shocks in compact red quasars?

Red quasars exhibit a higher incidence of compact (galaxy-scale or smaller) radio emission than blue quasars, arising from systems near the radio-loud/radio-quiet threshold. This result cannot be fully explained by the standard orientation model, instead favouring red quasars as a distinct phase in a quasar’s lifecycle, possibly an obscured-to-unobscured transition where low-power jets and/or AGN-driven winds drive away gas and dust. Previous work has focused on classifying radio morphologies of red and blue quasars in one radio frequency band, but radio emission can differ significantly across frequencies, with lower frequencies probing older electron populations.

For optically selected red and blue quasars, I compare radio morphologies across 3 surveys (FIRST: 1.4 GHz; VLASS: 3 GHz; LoTSS: 144 MHz) and find red quasars are significantly less likely than blue quasars to show extended low-frequency radio emission, suggesting fewer episodes of past activity and a younger evolutionary stage. Red quasars compact in all 3 surveys show the highest radio detection rates, and a striking excess over typical quasars of detections with steep radio spectral slopes $\approx -1$, consistent with an AGN-driven wind shock model. Additionally, I find a connection between the amount of dust and the production of radio emission, with the fraction of sources with shock-like radio spectral slopes increasing toward higher levels of dust extinction. I suggest these compact red quasars represent a young, “dusty blow-out” phase, where a compact jet and/or AGN-driven winds interact with a dusty ISM, causing shocks, leading to steep spectral slopes and enhanced radio detection rates.

232 Constraining AGN tori at cosmic noon using high-resolution JWST imaging and simultaneous SED fitting

There is an evidence for significant evolution in the gaseous and dust properties of galaxies since the era of cosmic noon (z~2). It is also well known that supermassive black holes co-evolve with their host galaxies, suggesting a constant connection between the small-scale (nuclear) and large-scale regions of galaxies. A fundamental component of AGN is the ``torus'' -- a dense, dusty structure that acts as the interface between the accretion disc and the ISM of the host galaxy. One may speculate that the transitional nature of the torus makes it a prime subject to search for evolution since cosmic noon. In this work, we use high resolution near- and mid-IR imaging from the JWST's CEERS to disentangle the emission from the torus in unprecedented detail in 88 X-ray selected AGN at z~2. Combining low-resolution multi-band photometry at UV to FIR wavelengths, from CANDELS and HELP, with the high-resolution JWST photometry, we employ a novel SED fitting method to constrain essential AGN and torus parameters, such as accretion disc luminosity and torus covering fraction. Despite the well-known evolution of the ISM and structural properties of AGN hosts from these redshifts, our population-level analysis finds no clear evidence for the corresponding evolution of the torus when compared to similar local AGN.

233 The role of AGN feedback in z~7 galaxies with JWST/NIRSpec

AGN feedback has become a key focus of galaxy evolution studies, due to the discovery of quiescent galaxies up to z～7 demonstrating that AGN feedback is required earlier in cosmic time than previously thought. Although JWST has now revealed a larger-than-expected population of AGN at z>4, their influence on their host galaxies’ evolution remains under debate: Does the main impact arise through a rapid ejection of gas via outflows, or through long-term cumulative feedback? I will present results from the analysis of new JWST/NIRSpec IFS data on two z∼7.6 low-mass (M ~ $10^8$ $\text{M}_\odot$, Curti+23) AGN host candidates lensed by a cluster. These AGN candidates were identified based on high-ionisation lines. The exquisite, deep IFS data shows spatially-resolved ionised gas kinematics via the [O III]λ5007 emission line; by identifying faint broad wings in the [O III]λ5007 profile, we infer the presence of galaxy-wide outflows, and explore spatially-resolved outflow properties of moderate-luminosity AGN at z>7 for the very first time. I will present a unique application of gas kinematic modelling to these galaxies, aiming to untangle outflows from galactic rotation. I will place constraints on the outflow properties, discussing the extent to which the observed outflows may be driven by star formation. Lastly, I will discuss the impact of the AGN feedback on the evolution of these high-redshift galaxies, with the aim of situating my results in a wider context to reveal how the impact of AGN feedback varies across cosmic time.

234 Role of AGN in galaxy evolution in z~3-11 in JADES deep spectroscopy

AGN feedback remains a vital path for the quenching of galaxies in theoretical models. With the recent discovery of quiescent galaxies at z>3, identification of typical moderate AGNs at high redshift became more essential than ever, to explain the ever-growing population of quiescent galaxies. As typical selection techniques such as X-ray and radio observations are not sensitive enough to detect the typical AGN population at high redshifts (z>3), we need to rely on optical emission lines, which are not accessible to astronomers at these redshifts until the launch of JWST. However, typical selection techniques using optical emission lines (such as BPT diagram), fail to reliably select AGN due to low metallicities of galaxies at high redshift, hence the need to revisit AGN selection.

In this talk, I will present the results from the JWST Advanced Galactic Survey (JADES) and its deep NIRSpec/MSA observations of 500 galaxies between z~3-11. I will describe the selection of AGN host galaxies at high-z using these emission lines, to reliably distinguish between star-forming and AGN host galaxies. Using this unique state-of-the-art dataset, I will present the first characterisation of moderate luminosity AGN, the AGN driven outflows and their host galaxy properties (such as black-hole masses, star-formation rates, stellar mass, etc.) at high redshifts, tracing the AGN feedback in the first 3 billion years of Cosmic evolution. Lastly, I will present the analysis of deep JWST/NIRSpec and ALMA observations of a quiescent galaxy at z~3 to constrain its quenching pathway via strangulation.

235 The FLARES view of early AGN

A key question in our understanding of super-massive black holes (SMBHs) and active galactic nuclei (AGN) is how they first formed and how they subsequently impacted their hosts. This is one of the objectives of the First Light And Reionisation Epoch Simulations (FLARES), a novel suite of hydrodynamical cosmological zoom simulations. The FLARES strategy allows us to simulate much larger effective volumes than possible with traditional periodic box methods, making it ideal to study the formation and evolution of AGN in the distant Universe.

In this talk I will introduce insights from the first iteration of FLARES (FLARES-EAGLE). I will begin by exploring predictions for the physical properties of SMBHs, and their hosts. I will also discuss the impact of SMBHs on their hosts using insights gained through matched simulations entirely without AGN feedback, or other modelling changes.

Finally, I will introduce a new AGN emission model, combining disc, BLR, NLR, and torus components, incorporated into the open-source synthesizer synthetic observations pipeline. When coupled with FLARES or other simulations, this allows us to predict the rest-frame X-ray to far-IR emission, including line emission. This enables us to make direct comparison with observational surveys, avoiding the need for complex and poorly motivated completeness corrections.

Speaker: Aswin Payyoor Vijayan (University of Sussex)

10:10 Final Discussion and wrap-up

Chandra and XMM-Newton at 25 - Utilising Several Decades of X-ray observation

Organisers: Norman Khan, Erwan Quintin, Robbie Webbe, Hui Yang

The X-ray observatories XMM-Newton and Chandra were both launched in 1999, and have been observing near continuously in the 25 years since. Their ability to complement each other has allowed the community to study the X-ray Universe in great detail. In concert with other X-ray instruments, and those in other bands too, the two together have helped to drive X-ray astronomy forward in leaps and bounds over the last two and a half decades.

In this milestone year this session aims to explore what can be, and has already been, achieved with this wealth of information, including the science products and source catalogues, combined containing more than 1,000,000 sources. Once combined with the observations of other instruments like Swift (which celebrates its own 20th anniversary in 2024), RXTE, eROSITA, etc., the community has access to more than half a century of observations of the soft X-ray sky. This session will showcase research that has been conducted using these vast archives, be it population studies, using advances in AI to mine for previously undiscovered phenomena, or developing tools to support the next generation of observatories. We will also bring together experts to discuss new ways in which they can be further exploited to brighten the future of X-ray astronomy.

With the next planned X-ray observatory, Athena, still at least a decade away, and AXIS and others still awaiting adoption, leveraging the results of XMM-Newton, Chandra, and others to maintain a vibrant X-ray community has never been more important.

236 XMM-Newton catalogues and data products after 25 years of observations

XMM-Newton has now been surveying the X-ray, ultra-violet and optical sky for 25 years. During this presentation I will talk about the data reduction and analysis software, the Science Analysis System (SAS) and automated pipeline processing of the data, along with recent improvements that have been implemented to maximise the science return of XMM-Newton and provide alerts for newly detected transients. I will also showcase the various XMM-Newton catalogues stemming from both pointed and slew observations and highlight some scientific results stemming from the exploitation of the catalogues. I will also present the upcoming 5XMM catalogue which will include many new products such as spectral fits, upper limits, source classification, photometric redshifts, long-term variability information and much more.

237 Uncovering Hidden Extragalactic Flares and Dips from the Chandra Archive with Machine Learning

We present a novel representation learning method for downstream tasks like anomaly detection or unsupervised classification in high-energy datasets. This enabled the discovery of a new extragalactic fast X-ray transient (FXT) in Chandra archival data, XRT 200515, a needle-in-the-haystack event and the first Chandra FXT of its kind. Recent serendipitous discoveries in X-ray astronomy, including FXTs from binary neutron star mergers and an extragalactic planetary transit candidate, highlight the need for systematic transient searches in X-ray archives. We introduce new event file representations, $E-t$ Maps and $E-t-dt$ Cubes, that effectively encode both temporal and spectral information, enabling the seamless application of machine learning to variable-length event file time series. Our unsupervised learning approach employs PCA or sparse autoencoders to extract low-dimensional, informative features from these data representations, followed by clustering in the embedding space with DBSCAN. New transients are identified within transient-dominant clusters or through nearest-neighbor searches around known transients, producing a catalog of 3559 candidates (3447 flares and 112 dips). XRT 200515 exhibits unique temporal and spectral variability, including an intense, hard $<$10s initial burst, followed by spectral softening in an $\sim$800s oscillating tail. We interpret XRT 200515 as either an unusual magnetar flare observed at low X-ray energies or the first extragalactic Type I X-ray burst from a faint, previously unknown LMXB in the LMC. Our method extends to datasets from other observatories such as XMM-Newton, Swift-XRT, eROSITA, Einstein Probe, and upcoming missions like AXIS.

238 Galactic Correlates of Supermassive Black Hole Growth from 25 Years of Chandra and XMM-Newton Cosmic Surveys

The co-evolution of supermassive black holes (SMBHs) and galaxies can be effectively constrained through sample-based analyses of the galactic correlates of long-term SMBH growth. Relevant correlates include stellar mass (M$_*$), star formation rate (SFR), and compactness. The sample-averaged SMBH accretion rate (BHAR), which constrains long-term SMBH growth in galaxy populations of interest, is measured using Chandra and XMM-Newton surveys data covering the standard "wedding-cake" design in sensitivity vs. solid-angle discovery space - including the Chandra Deep Fields, XMM-SERVS, COSMOS, and eFEDS. We have been advancing such investigations using partial-correlation analyses and complete, high-quality samples now reaching 8100 AGNs in 1.3 million galaxies, and I will briefly summarize some key findings. Specifically, (1) for the general galaxy population at z = 0.1-4, SMBH growth correlates most strongly with M$_*$; (2) for bulge-dominated systems, a strong BHAR-SFR correlation is observed, indicating synchronized growth between SMBHs and bulges; (3) BHAR also clearly correlates with galaxy compactness among star-forming galaxies, likely due to enhanced nuclear gas density for compact galaxies. Furthermore, combining these empirical correlations with large-scale numerical simulations of galaxy evolution enables improved tracking of SMBH growth through accretion and mergers across cosmic history. This approach provides insights into the evolution of the SMBH mass function, the SMBH mass-M$_*$ scaling relation, the relative importance of accretion and mergers to overall SMBH growth, and long-lived wandering SMBHs. Such studies will soon be substantially extended by combining the massive Chandra, XMM-Newton, and eROSITA archives with surveys by Rubin, Euclid, Roman, Xuntian, and new spectroscopic facilities.

Speaker: William Brandt (Penn State University)

Brandt-NAM-Correlates-01.pdf

239 Streamlining Galaxy Cluster X-ray Measurements with XGA and DAXA

The first eROSITA All-Sky Survey (eRASS-1) yielded a wealth of galaxy clusters across the sky. With the public release of this data in February 2024, the need for tools to automate and streamline large sample analysis became imperative. We present a sample of approximately 100 galaxy clusters detected by the Dark Energy Survey’s (DES) redMaPPer algorithm, eROSITA source detection, and in XMM observations by XCS (X-ray Cluster Survey). We provide an independent measure of eROSITA X-ray temperatures obtained using the newly developed open source Python modules XGA (X-ray: Generate and Analyse) and DAXA (Democratising Archival X-ray Astronomy). These software shield the user from the wearisome interactions with various telescope specific software, thereby streamlining X-ray analysis pipelines and making the generation of advanced X-ray data products accessible to astronomers unfamiliar with X-ray analysis, as well as improving the reproducibility of results. This talk will provide an overview of these software tools, demonstrating their functionality, with a focus on the methodology of measuring galaxy cluster temperatures. Lastly we will compare XGA measured eROSITA temperatures to their XMM temperatures, with the aim to verify selection functions used in the cluster abundance cosmology pipelines within DES and Euclid.

240 The INTEGRAL Science Legacy Archive Unveiled

The international gamma-ray astrophysics laboratory, INTEGRAL, was launched in October 2002 and collected science data continuously for 22.2 years until March 2025. The traditional data storage and distribution archive was operated by the ISDC in Geneva throughout the mission's lifetime. The INTEGRAL Science Legacy Archive, ISLA, was beta released at the October 2024 INTEGRAL workshop, and now in its first official public version at the end of March 2025. ISLA aims to provide a new archive experience using a visual and science-based approach to the exploration of data products contained in the archive together with a direct interface that allows scientists of all backgrounds to analyze INTEGRAL data using Jupyter notebooks in the public analysis facility provided through ESA Datalabs. With ISLA we aim to both preserve this treasure of more than 22 years of high energy data gathered by INTEGRAL and to facilitate its use new generations of astronomers for decades to come.

241 NewAthena – the next decade of X-ray observation

NewAthena will be the European Space Agency’s next large X-ray observatory, planned for launch in 2037. It will have revolutionary capabilities enabled by the combination of a lightweight large collecting-area mirror, a high-resolution spatially resolved X-ray integral-field spectrometer, and a wide-field X-ray imager. This next-generation observatory will thus enable transformational progress across all areas of astrophysics in the next decade, building on the legacy of the last 25 years of X-ray observation with Chandra and XMM-Newton.

In this talk, I will provide an update on the status of the NewAthena study phase for the community. I will also discuss the broad range of science that NewAthena will enable – including the growth of supermassive black holes across cosmic time and their impact on galaxy evolution, the assembly of the large-scale structure of the Universe, the stellar lifecycle (and its endpoints), the equation of dense matter in neutron stars, and the astrophysical nature of neutrino and gravitational wave sources – with a particular focus on what we can learn from the last several decades of X-ray observation as we develop our plans for NewAthena (and how the community can get involved now!).

10:20 Poster Flash Presentations

Explosive Transients in the Present and Future Sky

Organisers: Aysha Aamer, Edward Charleton, Benjamin Godson, Joshua Pollin, Ana Sainz de Murieta, Xinyue Sheng, Ben Warwick

This session aims to explore the present and future sky of extragalactic transients. These explosive events provide invaluable insights into the universe’s most extreme environments, encompassing phenomena such as the diverse range of supernovae, tidal disruption events (TDEs), and superluminous supernovae (SLSNe). Beyond driving nucleosynthesis and shaping star formation, some of these events also serve as vital cosmological distance indicators.

Despite significant progress, many intriguing questions remain unanswered, and the arrival of extensive surveys like LSST and 4MOST promises to increase this discovery rate by a further order of magnitude. Simultaneously, a new generation of space missions (SVOM, EP) are already providing novel insights and challenges to our understanding of the high-energy regime. In this era of big data, machine learning and AI are being increasingly employed across various stages of survey pipelines, enabling more efficient and effective searches for these transients, but it is crucial to understand where these methods excel, and where they are limited.

The primary aim of our session will be to bring together members of the UK transient community to showcase new observational and theoretical results and current projects in the field. This includes talks on a broad range of extragalactic astrophysical transients to disseminate ideas and foster collaboration between those working across the complete spectrum of transient types, wavelengths, and messengers. We also encourage talks looking at the science being facilitated by current and future photometric and spectroscopic facilities to promote discussion on future projects.

242 A Photometric Approach to Type Ia Science

Type Ia supernovae (SNe Ia) have played an important role in both astrophysical and cosmological analyses. Traditionally, these analyses rely on precise spectroscopic measurements of either the supernova or its host galaxy. The Vera C. Rubin Observatory Legacy Survey of Space and Time is expected to begin operations in early 2026, and will discover and measure millions of SNe Ia. However, spectroscopy will be feasible for only a small fraction. To fully exploit the number of detected SNe Ia, the development of photometric analyses is required. In this work, we present a photometric approach to SN Ia science, using a sample of ~3,500 SNe Ia discovered by the Dark Energy Survey (DES). We estimate photometric redshifts from the SN light curves, using flexible priors on the light curves of the SNe. Our photometric redshift estimator produces a low ~3% catastrophic outlier rate and results in a sample of usable SNe Ia that is almost double the size of the DES sample with host spectroscopic redshifts. Furthermore, our approach enables studies of lower-mass host galaxies, a regime often underrepresented in spectroscopic surveys due to their faint apparent magnitudes. We present the first results of our photometric analysis and explore its astrophysical and cosmological implications.

Speaker: Nikolaos Shiamtanis (University of Southampton)

243 Understanding kilonovae using radiative transfer simulations

The detection of the kilonova AT2017gfo has provided us with a wealth of observations. However, to interpret these observations to obtain information about the underlying merger ejecta, including r-process nucleosynthesis, we are reliant on kilonova modelling. The majority of binary neutron star ejecta models considered when simulating kilonovae have been in 1D, or even idealised toy models, which have neglected the complexities related to hydrodynamics modelling. I will show that 3D kilonova radiative transfer simulations are critical, due to the asymmetric nature of these events, and will present results on a 3D simulation from hydrodynamical merger ejecta using line-by-line opacities from millions of r-process transitions. I will also highlight the necessity of accurate atomic data of r-process elements, for which experimentally obtained data is highly incomplete.

244 Probing for Magnetars with Late-Time, Multi-Wavelength Observations of SLSNe

One of the most promising models to explain SLSNe is the magnetar model. In this scenario, the spin-down energy from a rapidly-rotating neutron star is injected into the supernova ejecta via a pulsar wind nebula (PWN). The PWN both accelerates the ejecta and produces broadband emission that is absorbed and thermalized in the ejecta. Since the light curves of magnetar-driven SLSNe are indistinguishable from those produced by other scenarios, observations at late times are key to testing the magnetar model. I will overview some of the proposed late-time signals, including radio emission from the PWN and infrared/optical spectral lines from the photoionized ejecta, with a focus on what can be detectable with new and upcoming instruments such as JWST and ngVLA.

245 Ultraviolet Spectroscopy of a Luminous Fast Blue Optical Transient

The rare and mysterious class of event sometimes known as luminous fast blue optical transients, typefied by the event AT2018cow, has provided a steady stream of surprises over the past five years: they are extremely radio-luminous, highly X-ray variable, and at least in some cases they produce ultra-fast optical flares for months and leave behind a hot remnant. While the emission from these transients peaks in the UV at all epochs, the only UV spectrum obtained before now has been a low-S/N UVOT grism observation of AT2018cow. I will pretent the first HST spectrum of a LFBOT, using COS and STIS to provide simultaneous coverage over the entire FUV/NUV range, with <1 Angstrom resolution blueward of 2000 Angstroms. Surprisingly, the spectrum is almost a pure single-temperature blackbody with no strong transitions beyond ISM absorption features from the Milky Way and host galaxy. The lack of strong features calls into question most supernova-like models, pointing towards models in which virtually all material from the progenitor system remains bound in a hot and dense plasma surrounding the central engine.

246 A study on late time UV-emission in core collapse supernovae and its use on uncovering peculiar transients

Over time, core-collapse supernova (CCSN) spectra become redder due to dust formation and cooling of the SN ejecta. A UV detection of a CCSN at late times is thus atypical. Additionally, a late time UV detection of a peculiar transient can therefore provide diagnostics as to their nature. An example of this is AT2018cow, a peculiar transient that was still UV-bright four years after it was discovered.
A late time UV detection may be a sign of interaction between the SN ejecta and the circumstellar material (CSM) that was expelled from the progenitor star before the SN explosion. The UV luminosities and light-curves provide information about how and when the CSM was formed and can help constrain progenitor models.
We investigate what fraction of CCSNe are detected in the UV between 2--5 years after the explosion. We use a sample of 51 nearby CCSNe observed with the Hubble Space Telescope (HST) within 2-5 years of discovery. We find two point sources, with a low chance alignment probability, within the uncertainty region of the SN position,which are therefore likely related to the SNe, both of which are known to be an interacting SN. We compare these detections to models of UV emission of interacting CCSNe and the limited amount of late-time UV observations available for interacting CCSNe in the literature.
We conclude that late-time UV observations of CCSNe and peculiar transients are a valuable asset for investigating the local environments of CCSNe and uncovering the nature of peculiar transients.

10:15 Poster Flash Presentations

Common Nature of Physical Processes in Solar and Stellar Coronae

Organisers: Patrick Antolin, Simon Daley-Yates, Jack Jenkins, Sargam Mulay, Christopher Osborne, Aaron W. Peat, Alexander Russell

The Sun offers unique insight and observational applications to the detailed understanding of stellar physics. The Sun serves as both a benchmark and laboratory for stellar processes. High-resolution and novel observations allow for the investigation of magnetic structure, coronal heating, condensations, and solar wind, to name a few. The broader statistical studies of stellar events can assist in the understanding of patterns and extremes of solar phenomena.

Stellar statistics constrain the frequency of, and energy associated with, extreme events. These, in turn, offer insight into coronal energy release mechanisms with applications to solar physics. Flare statistics and prominence formation are of great interest to the solar community as it can assist in the constraint of the formation and properties of these phenomena.

Recent advancements in both simulation and observation are gifting us new insight into and understanding of the aforementioned phenomena. Bridging solar and stellar astrophysics, both theoretical and observational, is essential to the understanding of solar and stellar processes. This session will focus on:
o Linking stellar flare, superflare, and CME statistics to solar coronal energy release mechanisms.
o Studying stellar winds to refine solar wind models and vice versa.
o Exploring solar/stellar prominence and condensation formation and/or ejection mechanisms, and properties.
o Investigating novel trends in coronal heating to resolve solar and stellar physics questions.

This session aims to foster interdisciplinary collaboration, and leverage stellar data to advance solar physics while using solar theories as a framework to understand stellar processes.

247 Placing Solar Activity and Rotation in the Context of Other Sun-like Stars

The Sun is approaching a transition in magnetic activity that has been observed in many of its siblings. Sun-like stars sustain magnetism by dynamo-action, powered by the interplay of convection and rotation. Stellar magnetic fields enable the heating of their atmospheres to millions of degrees and drive magnetised stellar winds. These winds play a crucial role in the evolution of Sun-like stars by removing angular momentum during the main sequence, a process called magnetic braking. This causes Sun-like stars to gradually spin down from a few days to around a month. The Sun’s rotation period of 25.4 days and age of 4.6 billion years is near to where magnetized stellar winds appear to become less efficient, a state referred to as weakened magnetic braking. Given that a star’s rotational history is linked to its magnetic activity through dynamo-action, this transition in magnetic braking has implications for how we understand the long-term evolution of exoplanetary atmospheres. However, studying older Sun-like stars is challenging because they are faint, leading to a lack of observational constraints, particularly in terms of rotation period measurements from missions like Kepler/K2 and TESS. Despite these challenges, we have now entered a golden age for solar exploration, with missions such as NASA’s Parker Solar Probe and ESA’s Solar Orbiter providing new insights on the Sun and the solar wind. These missions enable us to better understand the Sun’s present-day magnetic braking which in turn informs rotation-evolution modelling and helps place the Sun in context with its siblings.

248 Modelling Time-Dependent Turbulent Electron Acceleration and Transport in Solar Flares via the Fokker–Planck Equation

Solar flares are explosive releases of magnetic energy stored in the solar corona, driven by magnetic reconnection. These events accelerate particles, generating hard X-ray emissions. However, the energy transfer process remains poorly constrained, with competing theories proposing different acceleration mechanisms, including magnetohydrodynamic (MHD) turbulence. We investigate electron acceleration and transport in flaring coronal loops by solving a time-dependent Fokker–Planck equation. Our model incorporates transient acceleration, simulating the effects of impulsive energy input, such as from a pulse or wave train, to emulate the dynamics of transient reconnection processes (e.g., oscillatory reconnection) at the loop apex. We compute the density-weighted electron flux, a diagnostic directly comparable to observed X-ray emissions, across the energy and spatial domains from the corona to the chromosphere. Additionally, we measure the electron response time scale, which is the time that electrons take to move from a steady energy level to another energy level after being accelerated by a pulse. We conduct a detailed parameter study to assess how variations in the acceleration region’s properties influence the results under a turbulent acceleration model. Our findings reveal that the density-weighted electron flux largely depends on the pulse shape used to accelerate electrons at the loop top. Furthermore, the response timescale for a flaring loop at 20 MK is less than 4 seconds, shorter than the temporal resolution of some instruments. We also demonstrate that the electron response delay is energy-dependent, increasing gradually for higher-energy electrons.

249 Fermi-LAT analysis of solar flare events

With the ongoing peak of the 25th solar cycle, the number of solar flare events is on the rise. This offers the perfect opportunity to study these phenomena in greater detail and understand the production and transport of high energy particles/radiations in interplanetary space. This is fundamentally important for space-weather predictions and protecting in-orbit assets. The multi-wavelength emission of energetic particles and photons during solar flare events provides an ideal natural laboratory for identifying precursors that could aid in predicting these powerful events.

In this study, we present the results of our analysis of Fermi-LAT observations of solar flare events over 17 years. Characterisation of the gamma-ray spectra for all solar flares since 2008 helps us distinguish different types of gamma-ray solar flares and helps us look for pre-cursor signals. We also extrapolate the best-fit spectra to the TeV/PeV energy range to test the prospect of observation with future Southern Wide-field Gamma-ray Observatory (SWGO) surface array detectors.

250 Sun-as-a-star flare observations with high-resolution telescopes

Stellar flares cannot be spatially resolved, which means that we have to extract complex three-dimensional behavior from a one-dimensional disk-integrated spectrum. Due to their proximity to Earth, solar flares can serve as a stepping stone for understanding their stellar counterparts, especially when using a Sun-as-a-star instrument in combination with spatially resolved observations. In this talk I will discuss a confined X2.2 flare and its eruptive X9.3 successor as measured by the HARPS-N Sun-as-a-star telescope. We further explore these relations by using the newly developed Numerical Sun-as-a-Star Integrator (NESSI) code to convert 20 high-resolution SST flares to full disk spectra for a statistical study on disk-integrated flare behavior. Our findings suggest common patterns in the disk-integrated spectra between flares of different strengths and locations that can be used to better interpret stellar flares without resolved context.

Speaker: Dr Alex Pietrow (Leibniz-Institut für Astrophysik)

251 Quantifying the Relationship Between the Magnetic Complexity of an Active Region and its Associated Quantity of Cool Material in the Corona.

The study of coronal rain and other cool materials observed in the Sun’s upper atmosphere is becoming increasingly important given their connection to the fundamental mechanisms of coronal heating, flaring and eruption. The widely accepted formation mechanism of the phenomena is through concentrated footpoint heating of coronal loops. This heating leads to a cyclical process known as the Thermal Non-Equilibrium (TNE) cycle, resulting in an over-density of material, causing a subsequent rapid cooling of the plasma and it's coalescence into coronal rain. The drivers of this footpoint heating are still unknown though it is generally hypothesised that there may be a strong link to the local magnetic complexity.

We present a large-scale study of the solar atmosphere spanning five years of SDO observations to find any existing relationship between the magnetic complexity and the amount of cool material observed associated with a particular region of the Sun. We make use of the Polarity Inversion Measure (PIM) to quantify the magnetic complexity of an Active Region (AR) using HMI data. The amount of cool material present in this AR’s corona is then calculated with AIA 304~\AA\, using the RFit/Deep Filter algorithms that allow to identify the cool and hot emission within the passband. This process is then repeated for over 800 active regions. We observe a strong connection between magnetic complexity and the amount of cool material in the Sun’s atmosphere, and discuss the implications for solar and stellar studies of magnetic activity.

252 Doppler Dimming and Brightening Effects in Solar (and Stellar) Prominences

We explored the impact that Doppler dimming and brightening effects from bulk motions of isolated structures have on the formation of Lyα, Hα, and Mgɪɪh line profiles. This study was carried out in the context of solar prominence physics, but will be applicable to different structures and/or in stellar contexts. We compared two regimes in which these effects manifest: when the prominence is moving radially away from the solar surface (radial case), and when the prominence is moving parallel to the solar surface (horizontal case). The latter of these has not been thoroughly investigated in recent decades. To do this, we analysed 13,332 sets of model profiles generated through the use of the 1D non-local thermodynamic equilibrium (NLTE) radiative transfer (RT) code Promweaver, built on the Lightweaver NLTE RT framework to mimic the behaviour and output of the 1D NLTE RT code PROM, with the addition of overlapping transitions and arbitrary bulk velocity fields. We found that the horizontal case can produce a much greater dimming or brightening effect than the radial case with velocities of similar magnitude. This implies that horizontal velocities need to be accounted for when attempting to do any sort of interpretation and/or forward modelling.

Speaker: Aaron W. Peat (University of Wrocław)

Forging the elements: Understanding chemical evolution and stellar populations across cosmic time

Organisers: Conor Byrne, Stephanie Monty, Ankur Upadhyaya, Louise Welsh; co organisers: Nathan Adams, Karla Arellano-Cordova, Andreea Font, Robert Izzard, Chiaki Kobayashi, Christopher Lovell, Katherine Ormerod, Vadim Rusakov, Aayush Saxena, Ragandeep Singh Sidhu, Charlotte Simmonds, Elizabeth Stanway

The origin and build-up of chemical elements in stars, dust and gas throughout the Universe is a fundamental question in modern astrophysics. Addressing this requires understanding stellar nucleosynthesis, stellar evolution and galaxy evolution across all epochs and length scales. Progress hinges on combining constraints from cutting-edge observational facilities with state-of-the-art theoretical models of stars, the Milky Way, galaxies, and the interstellar and intergalactic medium.

The advent of JWST has revolutionized studies of chemical and galactic evolution at the earliest epochs. Interpreting these observations requires advanced stellar, galactic and chemical evolution models encompassing many physical processes, including: nuclear and atomic physics, chemistry and dust formation. Combining and discussing the results from these different areas is necessary to forge a unified model of the early Universe.

One area in which models need refinement is accurately representing the conditions in the distant Universe. Observations of extreme stellar populations such as young, massive stars at low metallicity and future studies with ELT are valuable tools to bridge the gap between high- and low-redshift stellar populations. A close relationship between observations and models is essential; high-quality observations constrain models, while improved models provide better insight into early chemical and galactic evolution.

This session targets these open questions from observational and theoretical perspectives, involving stellar and galactic astronomers. Through short talks and focused discussion, we will bring together the considerable leadership and expertise of UK-based researchers in these fields, gain insight into uncertainties and limitations of data interpretation, and outline a roadmap to addressing these challenges.

09:00 Welcome and introductory remarks

253 Probing chemical enrichment in star-forming galaxies using oxygen and argon abundances

Galactic chemical enrichment mechanisms have primarily been constrained by alpha-enrichment ([α/Fe]) and metallicity ([Fe/H]) measurements from deep absorption-line spectra of individual stars in the Milky Way (MW) and some local group dwarf galaxies. At larger distances out to high-redshifts (z>2), such measurements are only possible from integrated light from galaxies, almost exclusively from massive early-types. For emission nebulae (originally through analysing the direct chemical abundances of Planetary Nebulae and HII regions in the Andromeda galaxy), we found that the oxygen-to-argon abundance ratio, log(O/Ar), vs Ar abundance, 12+log(Ar/H), is analogous to [α/Fe] vs [Fe/H] for stars. This unique diagnostic plane allows us to probe chemical enrichment from the integrated emission-line spectra of star-forming galaxies (SFGs), which are the vast majority of galaxies in the universe, with their fraction increasing with increasing redshift. Utilising this diagnostic window, at low redshifts (z<0.3) with Sloan-Digital Sky Survey (SDSS) observations of ~800 SFGs, we observationally show that galaxy chemical enrichment history is driven primarily by the interplay of core-collapse and Type Ia supernovae, and how the impact of prevalent chemical enrichment mechanisms varies with galaxy mass. With a smaller sample of 11 SFGs at higher redshifts (z~1.3-7.7) with JWST/NIRSPEC and Keck/MOSFIRE, we show that MW-like chemical enrichment processes occur at least out to z~4, beyond which rapid but intermittent star-formation may be at play. This new O & Ar abundance based diagnostic window for emission nebulae will enable us to reveal the unique fingerprints of galaxy chemical enrichment all the way out to cosmic dawn.

Speaker: Souradeep Bhattacharya (University of Hertfordshire)

254 Measuring chemical enrichment over cosmic time with the JWST EXCELS survey and DESI

A slew of results from JWST spectroscopy have allowed us to start constraining the chemistry of galaxies over the vast majority of cosmic time. Rest-frame optical NIRSpec spectroscopy has provided the community with a large sample of galaxies with strong emission lines. Simultaneously, a number of programmes has provided deep spectroscopy resulting in a few dozen galaxies with detections of crucial faint emission lines such as [OIII]4363 (e.g. Curti+2023, Nakajima+2023, +), which allow us to robustly constrain chemical abundances using the Te-method.

Simultaneously, the DESI survey is building up the largest catalogue of galaxy spectra in the nearby Universe to date. DESI probes significantly lower-mass and fainter galaxies than previous generations of large spectroscopic surveys (see e.g. Scholte+2024). This year, we will have access to samples of tens of thousands galaxies with [OIII]4363 detections which is an order of magnitude increase over the current number.

I will show results where we present newly detected high-z [OIII]4363 galaxies (2 < z < 8) observed as part of the JWST EXCELS survey, which provides some of the deepest JWST spectroscopy currently available. We combine these measurements with the new sample of local Te-abundances obtained from DESI. These results show (1) the great success of recent improvements of strong line metallicity calibrations, (2) chemical enrichment of multiple elements in the early Universe, and (3) the path ahead with these new data in the nearby and high-z Universe.

Speaker: Dirk Scholte (University of Edinburgh)

255 Constraining the Chemical Enrichment Pathways of Galaxies in the early Universe with JWST

Elemental abundance ratios provide a unique constraint on the rate of enrichment via different physical processes (e.g. CCSNe vs Type-Ia SNe), yielding insights into galaxy evolution, star-formation timescales and chemical enrichment. At $z>2$, most observations are sensitive to the oxygen abundance, though recent developments in methodology and the advent of JWST spectroscopy have enabled the measurements of additional elements (e.g., Fe, Ne and Ar) at these redshifts. I will present measurements of O, Fe, Ar and Ne abundances for star-forming galaxies at $2 < z < 6$ from the NIRVANDELS and JWST/EXCELS surveys. These results show clear evidence of O-enhanced non-solar abundance ratios (i.e., O/Fe and O/Ar) as expected for young systems in the early Universe. I will also discuss the remarkable agreement of high-redshift abundance ratios with chemical evolution models and Milky Way galactic archaeological data. Finally, I will comment on the importance and implications of non-solar abundance ratios on our understanding of the first galaxies.

256 Chemodynamical simulations of dust formation in the distant Universe

Detailed modelling of the formation and evolution of dust is important to explain the high dust content in z~7 galaxies observed with ALMA, as well as the carbonaceous dust in z~8 galaxies observed with JWST. The latter is particularly difficult to explain with our current theories of dust formation, which depend on Asymptotic Giant Branch (AGB) stars to be the main factories of carbonaceous dust. As a significant amount of metals are predicted to be locked inside dust grains, this may have a substantial impact on mass-metallicity relations and our understanding of early chemical enrichment. Therefore, we introduce dust into our cosmological chemodynamical simulations, focusing on dust production in the early universe. We trace the mass of carbonaceous, iron, and silicate dust grains in the ISM from initial conditions. We increase dust mass through production in core-collapse supernovae and AGB stars, and accretion from gas phase metals. We destroy dust through star formation, supernova shock waves and thermal sputtering. We then compare our results to high redshift observations to reproduce high dust-to-stellar mass ratios and the early 'carbon bump' indicative of carbon dust produced by AGB stars. We analyse particularly the impact of dust on the early chemical evolution of galaxies.

Speaker: Alice Ferreira (University of Hertfordshire)

257 Bursty star formation and the chemical enrichment of high-redshift galaxies

Recent JWST observations have revolutionised our understanding of chemical evolution and physical conditions in galaxies during the epoch of reionisation, revealing surprisingly compact morphologies, bursty star-formation histories, and intriguing chemical signatures. Accurate interpretation of these observations demands sophisticated theoretical frameworks that self-consistently integrate galaxy evolution, stellar nucleosynthesis, and radiative processes. In this context, the THESAN-ZOOM simulations—a suite of high-resolution cosmological zoom-in simulations that include advanced interstellar medium physics and fully coupled radiative transfer—provide an ideal laboratory to explore galaxy formation and chemical evolution from redshifts z=3 to z=12. In this talk, I present new results from THESAN-ZOOM, highlighting a dramatic increase in the burstiness of star formation towards higher redshifts, driven primarily by stochastic gas inflows from the intergalactic medium and frequent galaxy mergers. These intense starbursts substantially alter chemical enrichment pathways, causing significant deviations from local scaling relations, such as the fundamental metallicity relation, predominantly due to strong inflows of pristine gas onto galaxies experiencing transient episodes of quiescence ("mini-quenching"). Moreover, bursty star formation naturally leads to distinctive chemical phenomena, such as extreme nitrogen enhancement, arising from the preferential ejection of oxygen due to its shorter enrichment timescale during starburst events. Consequently, residual gas is enriched predominantly by delayed yields from intermediate-mass AGB stars. This scenario elegantly explains unusual chemical abundances observed in high-redshift galaxies using standard nucleosynthetic yields, without invoking exotic processes such as the formation of supermassive stars. These findings underscore the critical importance of directly coupling state-of-the-art theoretical models with cutting-edge observational data.

258 Dusty star-bursting galaxy at the Epoch of Reionisation with NIRSpec/IFS and ALMA

Thanks to the exquisite capabilities of ALMA observatory, we were able to study dusty galaxies at EoR through their dust continuum and FIR emission lines. With these observations, a rapid buildup of dust in the early Universe. Until the launch of JWST, studying the rest-frame of optical emission of these sources was out of reach for astronomers.

In this talk, I will present one of the first JWST/NIRSpec IFS data of a massive dusty star-forming galaxy at the Epoch of Reionisation. COS-3018 (Laporte+18, Witstok+22), a luminous dusty object at z~6.8, previously only observed using ALMA ([CII]158 microns, [OIII] 88 microns). These observations revealed a massive dust reservoir (log Mdust =7.9 Msol), challenging theoretical models on how to build such a dust mass so early in the Universe.

In this talk, I will present deep high-resolution JWST/NIRSpec IFS observations of rest-frame UV and optical continuum and emission lines, in combination with deep ALMA [CII] and [OIII]88micron observations and NIRCam photometry, which enable us a comprehensive look into the both cold and hot ISM, its ionisation source (AGN or metal poor starburst?), metallicity gradient, densities and full kinematics comparison of the hot and cold gas. Furthermore, I will present first evidence of nitrogen enrichment from small star-forming clusters observed at high redshift. Finally, I will answer the question: What is driving such an extreme production of dust and UV luminosity in this galaxy, starburst or AGN and how did this galaxy produce so much dust and metals so quickly?

259 Chemical Enrichment in Nebulae of High-redshift Galaxies.

Several studies reported unexpected abundances of C, N, O elements in metal-poor nebulae in the first billion years of the universe. As these elements are produced via different pathways and on different timescales, such features present a unique opportunity to learn about the early metal enrichment and beginnings of galaxy evolution. This study focuses on the galaxies exhibiting enhanced N/O abundances identified in archival JWST data using the direct temperature method. Our sample consists of robust abundance measurements at $z > 4$, where we consider both galaxies with strong rest-frame UV and optical emission lines probing different ionization regions. This allows us to investigate general trends in temperature and density of the high and low-ionization nebulae as a function of redshift. We place these high-redshift observations in the context of metal-poor galaxies by comparing them with the H II regions in the local universe and at low redshift. By comparing the measurements of C, N, O and alpha-element abundances (Ne, Ar) with photoionization modelling of different stellar populations we discuss possible mechanisms for producing the nitrogen signature and outline existing gaps in resolving this problem.

10:25 Poster Flash Talks

10:30 Coffee Break

11:00 Annoucements

Plenaries 3 - Wednesday

260 JWST as a New Voyager for the Giant Planets

The first three years of JWST scientific operations have provided a treasure trove of new discoveries in our Solar System. Not since Voyager’s Grand Tour have we had a facility capable of spatially-resolved infrared spectroscopy of the four giant planet systems with shared techniques and instrumentation, enabling a comprehensive comparative planetology of the gas and ice giants, their rings, and myriad icy “ocean worlds.” JWST is opening a new window for discovery, accessing spectral domains that were too dark, too cold, or simply overlooked in planetary mission design over previous decades. In this presentation, we review recent discoveries enabled by JWST, from a combination of guaranteed-time, early-release and guest-observer programmes.

For the atmospheres of the giant planets, JWST has detected previously unseen jet streams on Jupiter, revealed the chemical composition of the Great Red Spot and polar vortices, explored seasonally-reversing stratospheric circulations on Saturn, mapped the stratospheric chemistry and circulation of Uranus for the first time, and caught enormous storm activity on Neptune. Emissions from H3+, methane, and carbon monoxide from their ionospheres have revealed delicate wave patterns on Jupiter, never-before-seen structures on Saturn, and the discovery of H3+ on Neptune, providing windows onto magnetospheric processes shaping the wider systems. JWST spectroscopy has revealed the extreme crystallinity of Saturn’s rings, including the “heavy water” fraction, and filtered imaging is revealing radial trends in icy composition of rings and moons in both Ice Giant systems. JWST has also constrained the gases erupting from Io’s powerful volcanism, searched for (but not detected) evidence of Europa plume activity, discovered polar hydrogen peroxide and a tenuous CO2 exosphere on Ganymede, and revealed how CO2 ice is co-located with the chaotic terrains of Europa, implying a connection to the deep surface ocean. These new discoveries will help to shape the exploration from future giant planet missions, such as ESA’s JUICE mission, NASA’s Europa Clipper and Dragonfly, and future endeavours like Uranus Orbiter and Probe.

Speaker: Prof. Leigh N. Fletcher (University of Leicester)

261 The environmental dependence of star and planet formation over cosmic time

Observations of star forming regions in the solar neighbourhood provide the empirical foundation for our current understanding of star and planet formation. In this paradigm, gas is converted into stellar systems in an environmentally independent process which can be described by “universal” dense-gas-star-formation relations. The resulting stellar systems form in isolation, and there is minimal dynamical evolution of planetary architectures after they have finished forming and left their natal environment.

I will share recent results using the Galactic Centre as a laboratory to test this paradigm in conditions which are more cosmologically representative of the environment in which most stars in the Universe formed. We find that “universal” dense-gas-star-formation relations fail to describe the conversion of gas into stars — star formation is inhibited in collapsing gas clouds until they reach densities orders of magnitude higher than predicted critical densities. When star formation eventually begins, the proto-stellar densities are so high that stellar feedback is expected to destroy proto-planetary disks on ~Myr timescales — the epoch over which planets assemble the bulk of their mass.

These results point to a paradigm in which environment is a key factor determining the outcome of the star and planet formation process, and the evolution of the planetary system architectures, over cosmic time. I will end by discussing the potential implications of these results in the context of where we expect to find life elsewhere in the Universe.

Speaker: Steven Longmore (Liverpool John Moores University)

12:45 Lunch

Sandwiches, stars and space: the NAM public engagement lunch

Organisers: Robert Massey, Andy Newsam, Lucinda Offer

NAM 2025 brings together astronomers and space scientists at all career stages. A large fraction of our community see communicating astronomy with the public as an important part of their work, from giving occasional talks and media interviews to running science festivals. (According to the 2023 RAS Demographics and Research Interests of the UK Astronomy and Geophysics Communities, staff members in universities and research establishments typically spend around 5% of their time on public engagement activities).

In this lunch we will bring together this diverse group for informal conversations on good practice in public engagement, with invited local speakers inspiring attendees with an outstanding exemplar of work with children and young people.

We encourage all delegates at NAM to come to our lunch, whether you are a novice or an experienced practitioner, to join this conversation on sharing our inspiring science.

This session will be organised by RAS staff and members of the RAS Education and Outreach Committee.

Panel Discussion: The Future of UK Astronomical Instrumentation

Organiser: Kathryn Hartley; co organisers: Aurelie Magniez, Deborah Malone

In this lunchtime panel discussion, we will bring together leading experts from academia and industry to discuss the future of UK astronomical instrumentation. Discussions will include the role of instrumentation in addressing key astrophysical challenges, such as probing the early universe, studying exoplanet atmospheres, and mapping dark matter. We will focus on emerging technologies, interdisciplinary collaborations and the current challenges in astronomical instrumentation. We will then open the floor to questions from the audience.

Habitable World Observatory UK Involvement Planning and Discussion

Organisers: Jessica Doppel, Qiuhan He, David Lagattuta, Richard Massey, James Nightingale

NASA’s Habitable World Observatory (HWO), which is set to launch in the late 2030s, will transform our understanding of exoplanets and the potential for life beyond Earth. Its primary goal is to identify and directly image at least 25 potentially habitable worlds and use spectroscopy to detect chemical biosignatures, such as oxygen and methane, in their atmospheres. This mission has scope well beyond exoplanets, including stellar astrophysics, cosmology, and extragalactic astronomy.

The telescope will feature a 6.5-meter primary mirror with infrared, optical, and ultraviolet detectors across a broad range of wavelengths. It will also include sensitive spectrometers, coronagraphs for direct imaging, and space-based imaging quality and optics, enabling exquisite imaging of exoplanet atmospheres, biosignatures, and distant galaxies.

Now is the critical time to explore how to maximize the nation's involvement. The UK leads 3 of the 65 science cases being used to optimise hardware design, and UKSA are negotiating a (potentially substantial) contribution of an instrument - but which is not yet agreed. This session will serve as a forum for UK researchers to present science objectives, discuss engagement strategies, and identify key areas where the UK can secure a leading role. Topics will include exoplanets, stars, galaxy evolution, dark sector physics, and how HWO can complement other space missions and UK contributions to ground-based observatories.

Advancing Space Instrumentation and Low-Cost Mission Concepts

Organisers: Adam Amara, Steve Eckersley, Lucia Fonseca de la Bella, Hamish Reid; co organisers: Malcolm Dunlop, Oscar Gonzalez, David Hall, Beatriz Sanchez-Cano

The rapid evolution of space instrumentation and mission design is ushering in a transformative era for solar-terrestrial physics, planetary science, and astrophysics. With an increasing emphasis on affordability and innovation, the space science community is exploring cutting-edge technologies and low-cost mission concepts that promise groundbreaking scientific discoveries. Recent initiatives by the European Space Agency (ESA)—including the M7/F2 program, the forthcoming M8 and F3 calls, and the agile mini-Fast mission concepts—highlight the growing demand for advanced instrumentation and creative mission architectures. In parallel, the UK Space Agency (UKSA) is driving technological progress through its Enabling Technology Programme and bilateral Science and Exploration Programme, fostering international collaboration and the development of next-generation space science missions.

This session invites contributions from researchers, engineers, and mission teams engaged in the design and development of innovative instrumentation and low-cost missions. We particularly welcome discussions on instruments targeting solar-terrestrial physics, extrasolar astrophysics, and planetary exploration, as well as proposals for small satellite missions and other cost-effective approaches. This session provides a unique platform for Principal Investigators (PIs) to lead the charge on these transformative missions. By bringing together expertise from academia, industry, and space agencies, this session seeks to highlight the UK’s pivotal role in shaping the future of space science. Attendees will explore how technological advancements, strategic collaborations, and resourceful mission planning can deliver high-impact scientific outcomes. Together, we can unlock the full potential of low-cost space science and exploration missions.

262 UK Space Agency Programmes for Supporting Space Science and Exploration

The UK Space Agency is seeking to increase the frequency and diversity of opportunities for UK R&D teams in academia and industry to work on innovative instrumentation and software for international space science and exploration missions, spanning areas such as solar physics, fundamental physics, astrophysics and planetary science. Contributions to traditional large scale science missions may be complemented by smaller, faster, and relatively low-cost contributions which are nevertheless highly innovative. The Agency has adopted a number of approaches to support the UK community in this way: a number of technology development programmes to innovate and raise TRLs; the proposed new ‘mini F’ mission class in ESA‘s Science Programme; bilateral (or multi-lateral) opportunities with other space agencies around the world, funded through the UK Space Agency’s Science &Exploration Bilateral Programme and the International Bilateral Fund. This talk will cover the different approaches and how to engage with the existing programmes, along with an overview of the Agency's strategic plans for Space Science and Exploration in the future.

263 Opportunities and interfaces with the European Space Agency

The European Space Agency forms a central part of opportunities to understand the highest priority scientific questions in any field, in close collaboration and partnership with National funding agencies such as the UK Space Agency. In this talk, I will provide a brief overview of how the European Space Agency (ESA) interacts with scientific communities. I will discuss the Directorate structure of ESA, and the formal science-related input that community representatives input into ESA's Director General through the Working Groups and Advisory Committees. I will then discuss the opportunities to be able to get involved in community input, represent your community and engage with both the UKSA and ESA through that structure. Finally, I will discuss recent mission opportunities, calls and give a personal perspective on future opportunities to fly world-class mission concepts.

264 Beyond CCDs: CMOS image sensors for soft X-ray astronomy

Historically, charge-coupled devices (CCDs) have been the detector of choice for soft X-ray astronomy, successfully deployed on numerous missions over several decades, including XMM-Newton, Swift XRT, Suzaku, Chandra, and the upcoming ESA SMILE SXI mission. While highly successful, CCDs are particularly susceptible to radiation damage and must be operated at cold temperatures, typically around -100 °C.

For the upcoming ESA M7 candidate mission, THESEUS, it was determined that the focal plane of the SXI could only be cooled to approximately -40 °C, rendering CCDs unsuitable and necessitating alternative detector technologies. CMOS image sensors (CIS) have already proven effective for optical instruments, as seen in ESA’s flagship JUICE JANUS instrument. However, as of 2019, CIS technology lacked the full depletion and efficient charge collection required for high-performance X-ray spectroscopy, prompting further development.

In response, ESA engaged the Centre for Electronic Imaging (CEI) and Teledyne e2v (Te2v) to develop the world’s first bespoke X-ray-optimized CIS. Between 2019 and 2024, the CIS221-X sensor was designed, manufactured, and characterized. This 2 × 2 cm device achieves an energy resolution of 126 eV at 5.9 keV at -40 °C and meets all focal plane requirements except detector size. This talk will present the performance of the current sensor and the development of the next-generation 4.5 × 9 cm CIS321, which will enable the SXI on THESEUS and lead to the largest X-ray imaging array ever flown.

265 The M-MATISSE mission: Mars Magnetosphere ATmosphere Ionosphere and Space weather SciencE. An ESA Medium class (M7) candidate in Phase-A.

The “Mars Magnetosphere ATmosphere Ionosphere and Space-weather SciencE (M-MATISSE)” mission is an ESA Medium class (M7) candidate currently in Phase-A study by ESA. M-MATISSE’s main scientific goal is to unravel the complex and dynamic couplings of the Martian magnetosphere, ionosphere and thermosphere (MIT coupling) with relation to the Solar Wind (i.e. space weather) and the lower atmosphere. It will provide the first global characterisation of the dynamics of the Martian system at all altitudes, to understand how the atmosphere dissipates the incoming energy from the solar wind, including radiation, as well as how different surface processes are affected by Space Weather activity.

M-MATISSE consists of two orbiters with focused, tailored, high-heritage payloads to observe the plasma environment from the surface to space through coordinated simultaneous observations. It will utilize a unique multiple-vantage point observational perspective, with the combination of in-situ measurements by both orbiters and remote observations of the lower atmosphere and ionosphere by radio crosstalk between them.

M-MATISSE is the product of a large organized and experienced international consortium. It has the unique capability to track solar perturbations from the Solar Wind down to the surface, being the first mission fully dedicated to understand planetary space weather at Mars. It will revolutionize our understanding and ability to forecast potential global hazard situations at Mars, an essential precursor to any future robotic & human exploration.

266 DREAM: A CubeSat Mission Concept for Probing Electron-Scale Energisation Processes

Electron-kinetic processes are the final, crucial step in the dissipation of the highly complex turbulent plasma dynamics that are prolific in all space and astrophysical plasmas across the Universe. However, due to the nearly-collisionless nature of many space environments, a variety of distinct plasma processes can contribute to energising and regulating the thermodynamics of the electrons. The Distributed Receivers for Electron Astrophysics Measurements (DREAM) mission is an electron-astrophysics mission concept aimed at measuring the thermal properties, heating, and crucially energy exchange processes for electrons in interplanetary space. DREAM would employ a swarm of up to 11 CubeSats orbiting within a few kilometres of each other to form a distributed electron instrument in space. This distributed instrument would both be capable of characterising the 3D electromagnetic fluctuations present at electron-scales in the plasma and, using a novel electron sensor, provide fast and sensitive measurements of the field-particle correlation between the electrons and electromagnetic fields in phase space on-board the spacecraft. The novel measurements from DREAM will be highly complementary to the new multiscale plasma missions, such as HelioSwarm and Plasma Observatory, that are on the horizon; with DREAM providing the targeted electron-scale measurements necessary to disentangle the complex processes responsible for controling the thermodynamics and energising electrons in the nearly-collisionless regime.

267 The Short-wavelength Camera for SOLAR-C EUVST

SOLAR-C is the third Japanese solar space mission, designed to provide a major advance over previous and existing solar missions. The main instrument of SOLAR-C is the EUV High-Throughput Spectroscopic Telescope (EUVST), which is complemented by the EUV Solar Spectral Irradiance Monitor (SoSpIM). EUVST will provide spectroscopic observations of solar atmospheric plasma from the 10,000 K chromosphere to the flaring corona (> 10 MK) simultaneously at very high spatial, spectral, and temporal resolution, thanks to its high efficiency (throughput) and unprecedented wide wavelength coverage. The EUV irradiance monitor will make novel flare observations and provide important information on the absolute calibration of EUVST.
The spectrograph consists of one short wavelength (SW) CCD camera (under development by ESA/UCL-MSSL), three long wavelength (LW) CMOS cameras and a slit-jaw imager (under development by NASA/NRL/LMSAL). In this presentation we describe the SOLAR-C mission objectives and capabilities, with an emphasis on the design and status of the SW camera development, including science performance expectations.

Speaker: Sarah Matthews (UCL)

268 Space qualifying the Image Slicer Technology for EUV applications

Image slicers have undergone significant progress for use in the space sector. However, the current solutions do not meet the required specifications for the next generation of space missions. Outstanding science questions require higher resolutions and sensitivity with reduced weight within minimum dimensions and at a low cost. Image slicers have never observed in the Extreme Ultra-Violet (EUV), a spectral range that contains emission lines which enables the study of particle acceleration, a fundamental process throughout the universe arising in: the Sun, active galactic nuclei, black holes, gamma ray bursts, planetary magnetospheres, neutron stars and accretion disks. Observing in the EUV introduces additional challenges such as: low photon flux, low reflectivity of coatings and the sensitivity of detectors.
Our project LUCES focussed on the space qualification of the image slicer technology for space application to enable integral field spectroscopy in the EUV. The application of this technology in the next generation of solar space missions will create 2D spectral images in seconds, over two orders of magnitude faster than the status quo. We present the unprecedented improvements achieved in slicer width and surface roughness for glass and metallic slicers, applicable to all spectral ranges. We will show the first multi-layer dielectric coating used on slicer mirrors. Finally, we will discuss the next steps towards space qualification and the application to a compact, high efficiency, high resolution solar integral field spectrograph for space: SISA. These developments can be applicable beyond solar physics, including HWO and many other sciences cases and missions.

269 Re-creating total solar eclipses in Space. The Moon-Enabled Sun Occultation Mission concept MESOM

The study of the solar corona has important ramifications on the understanding and forecasting of space weather phenomena. Yet, regardless of scientific breakthroughs brought by space-based coronagraphs, access to the lowest layers of the Sun’s atmosphere remains possible mostly during rare and sporadic total solar eclipses on Earth. This talk introduces the UK-led Moon-Enabled Sun Occultation Mission concept (MESOM), which capitalizes on synodic resonant orbits in the Sun-Earth-Moon four body problem to enable global and high-quality measurements of the inner sun corona below 1.02 sun radii. Our preliminary trade-off analyses show that a mini-satellite platform can reproduce total eclipse conditions in space once every synodic month (e.g., 29.6 days) and for 15 minutes on average, i.e., three times longer than the average eclipse duration on Earth, without image degradation caused by the Earth's atmosphere. With a nominal science operation plan of 2 years, MESOM could collect the equivalent amount of data of roughly 80 eclipses on Earth, making it a once in a life-time opportunity for deepening our understanding of the sun and its atmosphere.

Community EDI initiatives in Astronomy and Geophysics

Organisers: Katrine Glasscock, Marieta Valdivia Lefort, Laura Wolz; co organisers: Dominic Bowman, Andrew Curtis, Karen Devoil, Benjamin Fernando, Farideh Honary, Kirushney Kalamohan, Robert Massey, Nathan Mayne, Ingrid Murray, Jasmine Sandhu, Jane Smith, Matthew Temple, Luis Welbanks

A persistent challenge in Equity, Diversity, and Inclusion (EDI) is creating spaces to exchange ideas, share successful initiatives, and start critical conversations that foster meaningful change. The fields of astronomy and geophysics face widespread issues, such as imposter syndrome, balancing family life and the transient nature of research posts, and bullying and harassment. These issues significantly impact the ability to attract and retain diverse scientists and create inclusive workplaces. Addressing these challenges requires evidence-based, localised EDI practices that consider intersectional perspectives and support underrepresented groups, including LGBTQ+, ethnic minorities, disabled, neurodiverse, and first-generation scientists.

This session invites contributions from individuals who have designed and hosted impactful EDI projects or community events, such as EDI forums, EquiTea, and online platforms, aimed at improving equity and accessibility within their institutions. We encourage participants to share best practices for planning, delivery, and evaluation of EDI initiatives, as well as resources to support sustainable change. By showcasing the experiences and successes of our community, we aim to spark meaningful conversations and empower the astronomy and geophysics communities to build more equitable and supportive spaces.

14:15 Prep time

270 Isaac Physics & STEM SMART: Securing a diverse and inclusive future for physics and astronomy

A future for physics and astronomy that is diverse and inclusive requires early interventions to ensure underrepresented groups feel confident, encouraged and empowered to study STEM courses at university. Data shows that A level attainment is a barrier to entering competitive universities, even at institutions that make contextual offers, and that students from disadvantaged and certain ethnic minority backgrounds are awarded proportionally fewer top grades. We will present the results of an independent evaluation of the impact of two programmes, Isaac Physics and STEM SMART, on sixth formers aspirations, attainment and success in securing places at top universities.
Using stratified sampling of UCAS applicants to construct demographically matched control groups, results show that Isaac Physics and STEM SMART engage under-represented groups at levels well above the national average (e.g. ~40% women physicists compared with 23% taking A level physics, ~57% of the students are from the lowest 40% deprivation) and positively impact all under-represented groups in all three of their objectives with improvements of on average a grade for highly engaged students.

271 Evidence-based EDI: advancing equity, diversity and inclusion in outreach; learnings from the International Astronomical Youth Camp

The International Astronomical Youth Camp (IAYC) is a 3-week camp which has been
broadening the horizons of young adults since 1969. Using astronomy as a medium for
scientific inquiry, the IAYC has effectively engaged with 1000s of participants across more
than 55 camps. The participants range from 16-24 years old and come from a broad range
of backgrounds (e.g. academically and culturally).

Equity, diversity and inclusion have always been at the heart of the IAYC. Applicants have never been assessed on merit, but rather motivation, and we continually monitor and evaluate representation and bias within our application processes.. Thus far, we have studied the demographics of our participants (arxiv.org/abs/2111.08783); and we have examined how the cost can impact equitable participation in outreach activities (arxiv.org/abs/2106.02580). We also have a non-research programme as part of the camp which has included a range of EDI focused activities including an annual pride celebration, talks on imposter syndrome, and discussions on disability and accessibility.

We will present results from our previous research and how we have seen this evolve over the years; our initiatives to engage people from a wider range of backgrounds; and our ongoing work to maintain an inclusive environment within the camp for participants of all backgrounds. We will discuss the successes and challenges we have encountered and how we hope others can learn from our experiences to improve their own outreach activities.

272 A Case for Change: Inclusive Science Education through the Surrey Physics Academy

Persistent inequities in astronomy and physics continue to marginalise students from underrepresented and disadvantaged backgrounds. In this session, I present the Surrey Physics Academy — a grassroots initiative designed to widen participation and foster belonging through inclusive, community-driven science education.

Launched in 2022, the Academy delivers co-created summer schools, public engagement, and sustained outreach with a focus on girls, first-generation, ethnic minority, and neurodiverse students. The approach centers on local context, student voice, and collaboration with schools, charities, and science organisations.

This case study shares lessons learned in designing, delivering, and sustaining inclusive practice without core funding. I will reflect on the challenges of embedding equity into institutional culture and invite discussion on how similar models can be adapted across the astronomy and geophysics communities.

273 EquiTea at JBCA

Students at the Jodrell Bank Centre for Astrophysics within the University of Manchester have been running EquiTea sessions since 2022, inspired by Ares Osborn’s 2021 NAM talk ‘Creating EquiTea’. We have had over 20 speakers deliver talks or workshops on a range of EDI matters, which are followed by informal discussions about the topics raised. EquiTea has two founding statements: the observation that Physics and Astronomy is not equally accessible for all people from all backgrounds; and that by initiating discussion and engagement we can increase awareness and understanding, generating meaningful change.

This talk will explain the purpose and structure of EquiTea, then reflect on lessons learnt from 4 years’ experience of this community-led EDI initiative. Feedback from members of the department has been very positive, indicating that it has increased perceptions of safeness and welcomeness, and highlighting that EquiTea provides a platform to share minority and diverse lived experiences. Attendance has been good, primarily among early career researchers. Funding has been unstable, but our experience has been that we are able to function well without financial support.

The committee that organises EquiTea is eager to network with EDI initiatives at other UK departments. We would like to exchange ideas which engage audiences beyond those already involved in EDI discussions. We are aware that the size of JBCA allows us greater resources to run initiatives such as EquiTea, we are therefore interested in exploring ways of advancing the causes that motivate EquiTea beyond our own department.

274 Inclusive Pedagogy as an EDI initiative - a case study from the University of St Andrews

Within Higher Education, the boundary between “research” and “teaching” is increasingly blurred, given the (well justified) movement towards more authentic research experiences in undergraduate curricula. This contact with research (and researchers) can help undergraduate students develop scientist identities, at a time when they are often making decisions about whether to stay in academia and when they begin forming habits about how to think like a practicing scientist. It is, therefore, important to ask how our curricula are shaping the views of future scientists and how, as a sector, we engage in inclusive pedagogy.

I will present two cases from the University of St Andrews. The first is our institutional “Inclusive Practice Support Group”, which I co-founded in 2021. It is an interdisciplinary group of academic and professional services staff that meets three times per semester to discuss a topic of inclusive pedagogy (e.g. anti-racist pedagogy, intersectionality, queer pedagogy, inclusive assessment, public engagement and inclusivity, free speech, and many others). The second is a case study from a MPhys-level Cosmology module that I teach, where I address research practices within a wider social context in collaboration with students. In both cases I will highlight successes, challenges, and plans for the future.

Speaker: Rita Tojeiro (University of St Andrews)

15:18 Q&As

Solar Physics, Stellar Physics, and Exoplanetary joint session: bridging the gap

Organisers: David Brown, Malcolm Druett, Alex Pietrow, Don Pollacco, Angela Santos, Thomas Wilson

Understanding the formation, evolution, and behavior of our own Star and Solar System in a Stellar or Galactic context requires deeper coordination between solar and solar system investigations and the characterisation of stars and planets across the Milky Way.

The objectives of this session are:
(1) To bridge the gap between the stellar and solar communities, and between the exoplanet and stellar communities by bringing together experts to discuss the latest results in these fields.
(2) To provide a platform for collaborations and dissemination channels between the solar, stellar, planetary and exoplanetary communities.
(3) To provide an update about the PLATO mission (ESA’s next medium-class mission, which will continuously observe over 200,000 FGKM-dwarf stars with high cadence and quality for at least 2 years) and discuss its stellar and planetary characterisation potential.

We particularly encourage applications with relevance to the Sun-as-a-star, discoveries in Stellar physics with relevance to the Sun, advances in exoplanet discovery and characterisation, and Extreme space weather events and habitability such as:

Spatially resolved or Sun-as-a-star observations and models giving insight into mechanisms responsible for signatures in unresolved observations of stars, for example longer-term variations, flares, and other activity, and feature locations on the stellar disk.
Space weather observations and models with applications to understanding the environments and conditions around stars.

The latest findings regarding solar-type stars, including physical modelling, and stellar populations and the insights these can provide regarding behaviours that may occur on our local star and surrounding planetary environments.

Recent observations and modeling related to the spatially resolved images of nearby supergiants. How can the future of spatially resolved stellar observations help us to better understand the Sun?
Transit, radial velocity, and astrometry discovery and characterisation of terrestrial exoplanets particularly related to understanding the formation and evolution of these bodies.

Works related to the preparation and prospects for PLATO With the launch of PLATO in late 2026, this discussion is timely to highlight advances in the mission and galvanise the UK community to take full advantage of the data.

14:15 Prep time

275 Studying the solar-stellar connection through helio- and asteroseismology

Helioseismology uses the Sun's natural oscillations to infer properties about the Sun and its interior, while asteroseismology uses does the same for other stars. There are clear synergies between Sun-as-a-star helioseismology and asteroseismology in both observations and analysis techniques and thus helio- and asteroseismology are useful tools in studying the solar-stellar connection. In this talk, I will focus on a particular aspect of helio- and asteroseismology: the impact on the oscillations of magnetic fields. Magnetic fields change the properties of the oscillations used in helio- and asterseismology, including their frequencies, damping rates and amplitudes. I will detail how stellar activity cycles can impact the detectability of oscillations, which can, in turn, have an impact on exoplanet detections. I will also discuss the insights into solar and stellar magnetic activity that we can gain by studying how these parameters vary with time, including recent results that demonstrate how useful but underutilised high-frequency "pseudomodes" can be in this kind of study. Finally, I will describe how these magnetic-field induced variations can impact our ability to accurately determine stellar parameters, such as age, which is important in the context of the upcoming PLATO mission.

276 A Predictive Model for Solar and Stellar Irradiances: From the Sun to Exoplanetary Applications

Understanding the variability of stellar XUV irradiances is crucial due to their influence on surrounding planetary environments. The Sun provides the best laboratory for studying irradiance variability, driven by magnetic flux emergence and causing space weather effects. These variations strongly affect Earth’s ionosphere and thermosphere, influencing atmospheric expansion, satellite drag, and communication systems. However, despite continuous monitoring, solar irradiance measurements remain limited in wavelength coverage and long-term consistency, necessitating predictive modeling to reconstruct missing data.

To address this, we have developed a predictive model for spectral irradiances, initially calibrated using solar EUV/UV observations from SOHO/CDS and SDO/EVE, and correlated with solar activity proxies such as F10.7, F30, the Mg II index, and sunspot number. This model incorporates fundamental plasma parameters—chemical abundances, densities, and temperatures—using the latest atomic data from CHIANTI v.11, significantly improving irradiance predictions for transition region lines.

Extending this model to stellar atmospheres enables irradiance predictions for stars with limited or no direct measurements. Such advancements are critical for exoplanetary research, as stellar spectral energy distributions dictate planetary atmospheric chemistry, escape processes, and habitability. By bridging solar and stellar physics, this model provides a robust tool for characterizing exoplanetary environments and understanding how stellar activity influences planetary evolution.

277 Sun-as-a-star analysis of simulated solar flares

Stellar flares are a common type of stellar activity believed to have a strong influence on space weather. Since stars are too distant to be observed with sufficient spatial resolution as the Sun, studying the Sun provides a bridge to understand what could happen on other stars, especially solar-type stars. To relate the observations of the Sun with those of stars, one needs to use the Sun-as-a-star analysis, that is, to degrade the resolution of the Sun to a single point. In this talk, I will present the first Sun-as-a-star analysis of simulated solar flares with our 1D radiative hydrodynamics flare model and multi-thread flare assumption. We would also like to show how to diagnose the flare energy and location from observed spectra.

Speaker: Jie Hong (Stockholm University)

278 Sun-as-a-star Analysis of the X1.6 Flare on 2023 August 5: Dynamics of Postflare Loops in Spatially Integrated Observational Data

Postflare loops are important components of the standard flare model, and their existence has been suggested even in stellar flares. However, the spatially integrated data of postflare loops have not been fully investigated, and it is not yet clear how postflare loops are observed in stellar cases. To clarify behaviors of postflare loops in spatially integrated data, we performed the Sun-as-a-star analysis of the X1.6 flare that occurred near the northwest limb on 2023 August 5 using GOES (soft X-rays, $\sim10^7$ K), SDO/AIA (EUV, ≥$10^5$ K) and SMART/SDDI at Hida Observatory, Kyoto University (H$\alpha$, $\sim10^4$ K), focusing on postflare loops. As a result, this flare showed signatures corresponding to the important dynamics of the postflare loops even in the spatially integrated data: (1) Cooling of postflare loops was confirmed as peak time difference in soft X-rays, EUV, and H$\alpha$. Notably, the H$\alpha$ light curve showed two distinct peaks corresponding to the flare ribbons and the postflare loops. (2) Downflows were confirmed as simultaneous red/blue-shifted absorptions in Sun-as-a-star H$\alpha$ spectra. (3) Apparent rise of postflare loops was confirmed as the stop of the decay for the H$\alpha$ light curve. These results are keys to detect stellar postflare loops in multiwavelength observations and grasp their dynamics with spatially integrated data. We also discuss the dependence of our results on flare locations and its possible applications to stellar observations. Moreover, we mention the statistical study of postflare loops for further understanding of stellar flares.

279 Mitigation of radial velocity response to granulation by decorrelating with line shift and depth variations supported by MURaM simulations of the photosphere

Granulation in the stellar photosphere is a major limitation in achieving precise radial velocity (RV) measurements. Granulation-induced signals occur on timescales of tens of minutes, with amplitudes of ~1 m/s for Sun-like stars and tens of cm/s for later-type stars. We use synthetic spectra of stellar atmospheres generated by MPS-ATLAS from MURaM simulations of the photosphere, excluding magnetic activity. In a line-by-line approach, we measure variations in line depth and shift over a simulated time series of spectra. For both properties, we apply singular value decomposition (SVD) to model line responses to granulation. We use a reduced-rank representation with a small number of principal components, which serve as decorrelation vectors. The principal components reveal distinct line responses to granulation, depending on their formation temperature and atomic parameters. These decorrelation vector patterns vary significantly with spectral type due to differences in spectral line characteristics.
Similar line responses are observed in real data from the Sun and other stars. In particular, years of high-cadence observations with ultra-stable spectrographs provide ideal datasets for studying granulation. By applying the decorrelation vectors derived from synthetic spectra to a low-activity subset of HARPS-N solar data, we achieve a significant reduction in scatter in full-spectrum RV measurements. This approach to mitigating granulation-induced RV variations can be applied to other stars, improving RV precision and advancing the search for low-mass exoplanets.

280 Differential rotation of solar $\alpha$-sunspots and an extrapolation to other stars

Differential rotation is a key driver of magnetic activity and dynamo processes in the Sun and other stars, especially as they differ across the solar layers, but also in active regions. We aim to accurately quantify the velocity at which round $\alpha$-spots traverse the solar disk as a function of their latitude, and compare these rates to those of the quiet Sun and other sunspot types. We then aim to extend this work to other stars and investigate how differential rotation affects the modulation of stellar light curves by introducing a generalized stellar differential rotation law. This is achieved by tracking 105 manually identified $\alpha$-sunspots in the 6173~\AA continuum observed by the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO). This dataset, which represents over a decade of data allows us to derive a differential rotation law for $\alpha$-sunspots, which falls in between the rotation rate of quiet Sun and younger, and more complex sunspots. We extend this analysis to other stars by introducing a scaling law based on the rigid rotation rates of these stars. This scaling law is implemented into the Stellar Activity Grid for Exoplanets (SAGE) code to illustrate how differential rotation alters the photometric modulation of active stars. Our findings emphasize the necessity of considering differential rotation effects when modeling stellar activity and exoplanet transit signatures.

Speaker: Ms Emily Lößnitz (Leibniz-Institut für Astrophysik)

Theoretical and observational approaches to the Hubble tension

Organisers: Indranil Banik, Harry Desmond, Eleonora Di Valentino, Tom Shanks

Cosmology is currently in a crisis due to the Hubble tension, the observation that redshift rises about 10% faster with distance than predicted in ΛCDM with parameters calibrated to fit the CMB anisotropies. This session would bring together researchers working on various aspects of the Hubble tension. Recent observational advances allow distances to be measured in several ways beyond the traditional route using the Leavitt law and supernovae, while precise CMB results can now be obtained without Planck data. Besides the CMB, cosmological constraints have recently been provided by novel probes such as the dispersion measure of fast radio bursts, cosmic chronometers, and accurate estimates of the age of the Universe from the oldest stars. Proposed solutions to the Hubble tension either argue that distances in the nearby Universe have been systematically underestimated, raise the present expansion rate at the background level, or assign the steep local redshift gradient to peculiar velocities, as would arise from outflows due to a large local void – as indeed suggested by galaxy number counts and bulk flows. Solutions at the background level can modify the sound horizon at recombination, as done by early dark energy models. Or they can involve a late-time modification, possibly due to the dark energy density changing with time. This is actually suggested by the latest baryon acoustic oscillation data. The proposed parallel session would allow especially early career researchers working on these and other aspects of the Hubble tension to present their work and learn from each other.

281 The local void solution to the Hubble tension

A promising explanation for the Hubble tension is that we live near the centre of a large local underdensity or void. This is suggested by observations of source number counts across the whole electromagnetic spectrum, with near-infrared results implying that the density is about 20% below average out to 300 Mpc across 90% of the sky and most of the galaxy luminosity function (ApJ, 775, 62). Outflows from this KBC void can induce enough extra redshift to plausibly solve the Hubble tension with a standard background cosmology known to fit the CMB (MNRAS, 499, 2845). I will discuss various tests of this proposal. At low redshift, the bulk flow of galaxies traces the average velocity of matter within a sphere centred on our location. The observed bulk flow curve agrees well with the void model predictions (MNRAS, 527, 4388). Looking further out, it is possible to infer $H_0$ from data in a narrow redshift range centred on $z$. Such an empirical $H_0(z)$ curve agrees quite well with expectations in the void model, which predicts a return to the CMB-derived $H_0$ beyond the void (MNRAS, 536, 3232). This result is related to recently published work on baryon acoustic oscillations (BAOs), which show a deviation from ΛCDM expectations (MNRAS, 540, 545). I will explain how the BAO observables would be affected by a local void. I will then present BAO results compiled over the last twenty years. These results fit better if the local void is included, thanks to good agreement with ΛCDM at high redshift but a persistent anomaly at lower redshift, sometimes interpreted as due to evolving dark energy.

282 Tests of distance duality - Implications for the Hubble Tension

There have been several studies investigating the cosmological implications of the Hubble tension, both in terms of the impact on early and late universe physics. I will summarise some of our previous work on investigating late-time solution with the first simultaneous analysis of local and high-redshift Type Ia supernovae and exploring a wide range of exotic cosmological solutions. In this talk, I will then explore the impact of testing the distance duality relation - the relaiton between angular diameter and luminosity distances - on the Hubble tension. In our analyses we explore the impact of different data assumptions in the Type Ia supernova, baryon acoustic oscillation samples and explore the relation of the distance duality parameter to dark energy properties. Finally, I will summarise our findings on interpreting the results in terms of intergalactic dust properties.

283 A pathway to the Hubble constant via cosmic chronometry and machine learning with the GAMA survey

An alternative approach to resolving the Hubble tension that relies on minimal assumptions of cosmology and does not propagate the uncertainty associated with calibrations of the distance ladder is based on the relationship between the Hubble parameter $H(z)$ and the differential age-redshift relation. This relationship allows us to quantify the expansion between two coevolving populations of galaxies as $H(z) = -dz/dt(1+z)$ thus allowing us to constrain the value of the Hubble constant $H_0$. By taking the differential age dt and redshift dz rather than absolute values of enough pairs, the uncertainties associated with their calculation can be overcome to provide an accurate measurement of the Hubble parameter.

Populations of passively evolving galaxies are used as standard clocks, or cosmic chronometers (CCs), however due to their intrinsic nature they are rare. Their selection relies on spectroscopic observation and full spectral fitting which limits the number of detected candidates. Therefore, we present a machine learning based method to flag cosmic chronometer candidates based on their images so future spectroscopic surveys can target them for observation in order to confirm CC status, determine their ages and use them to calculate $H_0$. Our method utilises outlier detection with a convolutional autoencoder concurrently with a KMeans clustering algorithm to identify CC candidates from the Galaxy and Mass Assembly (GAMA) survey. Using this approach, we determine a novel value of $H_0$ at the redshift regime of $0.03

284 A Bayesian analysis of anisotropies in the redshift--distance relationship of clusters

The Hubble tension is a significant (~4 sigma) discrepancy between the universe's expansion rate measured from supernovae and the rate predicted by the standard ΛCDM cosmological model based on CMB observations. Inspired by this tension, more detailed analyses of late-universe data have also revealed possible large-scale variation in the redshift–distance relationship across the sky, based on measurements from various sources including supernovae, strong lenses and galaxies. In this talk we focus on the anisotropy in the distance--redshift relation of clusters at z~0.1, as measured by the normalisations of various scaling relations linking their properties. This anisotropy forms a dipole pattern, the axis of which is approximately aligned with the CMB dipole, the anomalous bulk flow of CosmicFlow-4, and the anomalous matter dipole seen in high-redshift quasars. I will present the early stages of a Bayesian hierarchical model reanalysing these results, with the aim of accounting self-consistently for all relevant systematics including the joint intrinsic distributions of the clusters' properties. I will ​show preliminary results ​indicating that ​there is in fact no dipole in the expansion rate from these observations​, and discuss implications for the Hubble tension.

285 A joint calibration of the distance ladder, the local velocity field, and inference of the Hubble constant

We pursue a comprehensive approach towards the estimation of the Hubble constant by addressing two separate but interlinked sources of uncertainty: peculiar velocities and the calibration of the distance ladder. Peculiar velocities introduce noise in the Hubble diagram and can potentially bias the Hubble constant estimates derived from direct distance tracers. Traditionally, their impact is mitigated by applying velocity field corrections inferred from separate analyses. Simultaneously, it is typically assumed that direct distance tracers are already calibrated. We propose a unified framework that jointly calibrates the distance ladder—starting from geometric anchors, through Cepheid and Tip of the Red Giant Branch measurements, to Tully–Fisher galaxies—while simultaneously calibrating the peculiar velocity field (which probes the growth rate of structure) and the Hubble constant. This integrated approach allows for a robust, self-consistent accounting of the effect of distance ladder calibration, peculiar velocities, and for a joint inference of both the growth rate of matter and the Hubble constant. In this talk, I will present a preliminary set of results.

Radio Astronomy in the build up to the SKAO

Organisers: Johannes Allotey, Emmy Escott, Catherine Hale, James McGarry, Lucy Oswald, David Williams-Baldwin

The field of radio astronomy will soon be revolutionised by the arrival of the Square Kilometre Array telescopes. Now that the first fringes have been recorded with SKA-Low, and the first SKA-Mid dish is in place, it is time to look to the future of radio astronomy and the scientific opportunities coming up, and to reflect on the state-of-the-art science with precursor/pathfinder telescopes.

The goal of this session is to showcase the breadth of work conducted with SKA precursor and pathfinder instruments, such as e-MERLIN, MeerKAT and LOFAR across a diverse range of science goals, and to provide an opportunity for discussion and connection over plans for future science with the SKA Observatory (SKAO). We also will likely include discussion from invited speakers to update on the SKAO and the Science Regional Centres.

The session will be organised and led by members of the SKAO UK Early Career Researcher (ECR) committee, and will build on the success of the equivalent session at NAM2023.

286 Detecting the Universe’s structure with the SKAO precursor MeerKAT in cross-correlation with galaxy surveys

Using the SKAO to map the intensity of neutral hydrogen’s 21cm emission line will be a golden opportunity to constrain models of cosmology. Neutral hydrogen will reside around peaks in the late Universe's underlying density field, the clustering of which is rich in cosmological information. I will present results from MeerKAT pilot surveys where the 64 single-dishes scan the sky in auto-correlation mode, providing 21cm intensity maps that cover ~200 square degrees at redshift z~0.43. We find strong correlations between the MeerKAT pilot survey intensity maps and overlapping galaxy catalogues from optical telescope surveys. This is strong evidence for detecting large-scale cosmic structure within the 21cm intensity maps since the galaxies are a known tracer of the underlying dark matter density field. The cross-correlations between 21cm intensity maps and optical galaxies are a powerful technique for understanding and mitigating systematics, allowing for cosmological signatures to be revealed, which are otherwise dominated by contaminants in the low signal-to-noise pilot survey data. This is the first time such detection has been made with an array of dishes operating in single-dish mode, validating the technique that will be used with the arriving SKAO. The SKA-Mid will also present an upgrade in sensitivity relative to MeerKAT. Furthermore, the Band 1 receivers will provide a deeper redshift range, meaning the volumes we can span in these maps will increase by several orders of magnitude. This will allow more precise constraints and larger scales to be probed, making the SKAO a powerful instrument for cosmology.

287 Prospects of a statistical detection of the 21-cm forest and its potential to constrain the thermal state of the neutral IGM during reionization

The cosmological 21-cm forest, a series of absorption lines in the spectra of high-z radio-loud sources arising from the hyperfine structure of neutral hydrogen residing in the intergalactic medium (IGM), has a potential to be a unique probe of the neutral IGM during the Epoch of Reionization. While there are no detections of this signal up to date, I will argue that the prospects of detecting the 21-cm forest signal are improving because of (1) recent evidence that reionization ended as late as z<5.5, (2) increase in the number of known high-z radio-loud quasars and (3) the improving radio telescopes such as the uGMRT and SKA. In this context, I will present our models of the 21-cm forest signal based on cosmological simulations, in which we simultaneously vary the X-ray background radiation efficiency and ionization state of the IGM. I will discuss the detectability of this signal by the uGMRT and SKA1-low, both direct detection of individual absorption lines and statistical detection. I will finish this talk by showing that the spectroscopical observations of the 21-cm forest signal provide a unique opportunity to constrain the cosmic heating and reionization history at z≥6 even in the case of a null-detection.

288 Non-thermal Radio Filaments in the Galactic Plane

Non-thermal radio filaments (NRFs) were first discovered 40 years ago in the Galactic Centre (GC) with their astrophysical origins still being a topic of debate. The SARAO MeerKAT Galactic Plane Survey (SMPGS) recently revealed a population of NRFs found throughout the Galactic Plane (GP). Confirming these would challenge NRF origin models that rely on the unique environment of the GC and could provide insights into Galactic cosmic ray source populations for the first time. Further study of these NRFs with the JVLA and MeerKAT is ongoing.

Whilst the existing data have given numerous promising results, the SKA will significantly advance these studies. Better sensitivity will allow for deeper surveys of the GP detecting fainter NRFs. Much improved angular resolution will enable more direct comparisons between the GC and GP populations — many GC filaments are only marginally resolved by the MeerKAT synthesised beam at L-band — and allow properties such as spectral indices to be resolved across the filament.

In this talk, I will summarise current knowledge of NRFs; the ongoing study of them using SKA precursor and pathfinder telescopes; and how the future capabilities of the full SKA will enable us to further constrain the filaments and their astrophysical implications.

289 RFI protection of the SKAO

Radio Frequency Interference is one of the most detrimental effects for radio astronomy. The SKAO takes the protection of the radio frequency spectrum in both sites very seriously, placing great effort in controlling our own activities, our equipment and the effects that external users of the radio spectrum can produce on our science.

This talk will describe the Spectrum Protection Office initiative at the SKAO, a group dedicated to the oversight of the control and mitigation of RFI ranging from RFI monitoring and RFI/EMC controls to Spectrum Management.

290 A striking signature of shocks in compact red quasars?

Red quasars exhibit a higher incidence of compact (galaxy-scale or smaller) radio emission than blue quasars, arising from systems near the radio-loud/radio-quiet threshold. This result cannot be fully explained by the standard orientation model, instead favouring red quasars as a distinct phase in a quasar’s lifecycle, possibly an obscured-to-unobscured transition, where low-power jets and/or AGN-driven winds drive away gas and dust. With the advent of SKA pathfinders such as LOFAR, we can probe lower radio frequencies than ever before, at high resolution and high sensitivity, while still retaining large sample sizes for population statistics.

For optically selected red and blue quasars, I compare radio morphologies across three surveys (FIRST: 1.4 GHz; VLASS: 3 GHz; LoTSS: 144 MHz) and find red quasars are significantly less likely than blue quasars to show extended low-frequency radio emission, suggesting fewer episodes of past activity and a younger evolutionary stage. Red quasars compact in all three surveys show the highest radio detection rates, and a striking excess over typical quasars of detections with steep radio spectral slopes $\approx -1$ , consistent with an AGN-driven wind shock model. Additionally, I find a connection between the amount of dust and the production of radio emission, with the fraction of sources with shock-like radio spectral slopes increasing toward higher levels of dust extinction. I will discuss the implications within the context of a potential quasar evolutionary model and outline future research directions with SKA to further constrain the origin of enhanced radio emission in red quasars.

291 LOFAR studies of radio-loud AGN: insights into the SKA era

The unprecedented sensitivity of wide-area, low-frequency radio surveys like the LOFAR Two-Metre Sky Survey (LoTSS) has uncovered a vast population of radio-loud AGN (RLAGN) previously missed by high-flux-density surveys such as the Third Cambridge Catalogue of Radio Sources (3CRR). As a key SKA precursor, LOFAR plays a crucial role in identifying these populations and advancing our understanding of the physical mechanisms driving RLAGN evolution.

Using 6-arcsec LoTSS DR2 (144 MHz) and 2.5-arcsec Very Large Array Sky Survey (VLASS, 3 GHz) data, we construct a flux-complete (>10 mJy), extended (>60-arcsec) sample of 2828 spectroscopically confirmed RLAGN (z<0.57) to investigate the relationship between emission-line and radio properties. We classify these sources into high- and low-excitation radio galaxies (HERG and LERG) and further categorise them into Fanaroff & Riley type I and II (FRI/FRII), wide- and narrow-angle tail (WAT/NAT), head-tail (HT), and relaxed-double (RD) morphologies. Additionally, we identify a subclass of remnant and restarted RLAGN within these morphological classes.

By analysing mid-infrared properties, host galaxy mass, and core prominence, we reveal the complex interplay between morphology, environment, and accretion processes. Our findings emphasise the need for a multi-dimensional approach to constraining RLAGN accretion modes—an effort that will be significantly enhanced by SKA’s unprecedented sensitivity and frequency coverage. This study highlights how SKA precursors like LOFAR are paving the way for next-generation radio surveys, setting the stage for transformative advances in AGN physics with the SKA Observatory (SKAO).

292 Strap on your Boötes: The Journey to Achieve Widefield Sub-arcsecond Resolution with LOFAR

Thanks to SKAO (Square Killometre Array Observatory) pathfinders, recent technological developments have allowed radio surveys to go deeper than ever before. One such example is the International LOFAR Telescope (ILT). The LOFAR Two-meter Sky Survey (LoTSS) Deep Field first data release provides us with 6” images at 144 MHz with sensitivities down to 20 μJy/beam using just the Dutch stations. This is just the beginning of what the ILT can achieve. Using Very Long Baseline Interferometry (VLBI) techniques, we can incorporate the international stations during the data reduction process, to produce sub-arcsecond resolution images.

Due to the ILT’s extensive field of view, we can produce widefield, high resolution images. These widefield images consist of billions of pixels and contain thousands of sources, each of which is at 0.3” resolution. However, this technique is challenging and very computationally expensive. To date, there are only two fully imaged fields, Lockman Hole and ELAIS-N1, at sub-arcsecond resolution (Sweijen et al. 2022, de Jong et al. 2024).

I will discuss the challenges that are faced when producing these images, including having to correct for differential ionospheric effects across multiple square degrees and starting self-calibration without knowing the source structure. I will present the first sub-arcsecond resolution image at 144 MHz of the Boötes Deep Field. Using this image, I will demonstrate the scientific potential of such widefield high resolution images.

The calibration knowledge gained by producing these images at such low frequencies will be critical or applying VLBI techniques to SKA-Low.

15:39 Poster Flash Presentations

Explosive Transients in the Present and Future Sky

Organisers: Aysha Aamer, Edward Charleton, Benjamin Godson, Joshua Pollin, Ana Sainz de Murieta, Xinyue Sheng, Ben Warwick

This session aims to explore the present and future sky of extragalactic transients. These explosive events provide invaluable insights into the universe’s most extreme environments, encompassing phenomena such as the diverse range of supernovae, tidal disruption events (TDEs), and superluminous supernovae (SLSNe). Beyond driving nucleosynthesis and shaping star formation, some of these events also serve as vital cosmological distance indicators.

Despite significant progress, many intriguing questions remain unanswered, and the arrival of extensive surveys like LSST and 4MOST promises to increase this discovery rate by a further order of magnitude. Simultaneously, a new generation of space missions (SVOM, EP) are already providing novel insights and challenges to our understanding of the high-energy regime. In this era of big data, machine learning and AI are being increasingly employed across various stages of survey pipelines, enabling more efficient and effective searches for these transients, but it is crucial to understand where these methods excel, and where they are limited.

The primary aim of our session will be to bring together members of the UK transient community to showcase new observational and theoretical results and current projects in the field. This includes talks on a broad range of extragalactic astrophysical transients to disseminate ideas and foster collaboration between those working across the complete spectrum of transient types, wavelengths, and messengers. We also encourage talks looking at the science being facilitated by current and future photometric and spectroscopic facilities to promote discussion on future projects.

293 The Search for ECLEs in DESI's Early Data Release

Extreme coronal line emitters (ECLEs) are a composite population of tidal disruption events (TDEs) and exotic active galactic nuclei (AGNs) displaying emission lines from highly ionised iron (FeVII - FeXIV). These lines are produced through the reprocessing of high energy X-ray photons by gas-rich environments. The TDE-linked subpopulation of these events also displays a distinctive mid-infrared flaring behaviour through additional emission reprocessing and show temporal evolution, returning to their quiescent / pre-outburst properties on timescales of years - decades. As such, ECLEs provide a unique opportunity to explore gas rich nuclear environments of both quiescent and active supermassive black holes.

Here I will report on the search for these objects within the early data release (EDR) of the Dark Energy Spectroscopic Instrument (DESI). DESI's goal of obtaining a vast number of spectroscopic redshifts of galaxies across the northern sky makes it an excellent tool in the search for ECLEs which given their rarity (~ 2×10−9 Mpc−3 yr−1) necessitate the use of large-scale surveys for discovery.

In my talk, I will summarise the ECLE search within DESI EDR, highlight the most promising objects identified (including detailing the follow-up observations conducted) and provide context into how this newly identified sample compares to our existing samples of ECLEs, TDEs and exotic AGN. I will also present the most current rate estimates of these objects based on the DESI search in combination with previous analyses based on SDSS and BOSS samples.

Speaker: Peter Clark (University of Southampton)

294 AT2019cmw: A highly luminous, cooling featureless-TDE candidate from the disruption of a high mass star in an early-type galaxy

We present Optical/UV photometric and spectroscopic observations, as well as X-ray and radio follow-up, of the extraordinary event AT2019cmw. With a peak bolometric luminosity of ~10^45.6 erg/s, it is one of the most luminous thermal transients ever discovered. Extensive spectroscopic follow-up post-peak showed only a featureless continuum throughout its evolution. This, combined with its nuclear location, blue colour at peak and lack of prior evidence of an AGN in its host lead us to classify this event as a “featureless” tidal disruption event (TDE). It displays blackbody evolution atypical of most TDEs, cooling from ~30kK to ~10kK in the first ~300 days post-peak, with potential implications for future photometric selection of candidate TDEs. We also do not find significant evidence of X-ray or Radio emission, placing constraints on the presence of on-axis jetted emission or visible inner-accretion disk. Our lightcurve modelling suggests that AT2019cmw may be the disruption of a star in the tens of solar masses by a supermassive black hole (SMBH). Combined with a lack of detectable star formation in its host galaxy, it could imply the existence of a localised region of star formation around the SMBH. With the expected discovery of >35000 TDEs by the upcoming Vera C. Rubin Observatory, this could provide a new window to probe star formation rates and the initial mass function (IMF) in close proximity to SMBHs out to relatively high redshifts.

295 A tidal disruption event that turned off

Tidal disruption events (TDEs) are rare transients that occur when stars are torn apart by black holes and accreted. At X-ray energies, they are typically soft, thermal sources that slowly evolve over years or even decades, or harder sources produced by relativistic jets that decay rapidly when the jet turns off. In this talk, I will discuss a unique source discovered in archival Swift-XRT data that, while clearly a TDE, does not truly match either of these pictures. LSXPS J0956 is a soft thermal nuclear transient that initially decays slowly before exhibiting a precipitous decline roughly two years after initial detection, similarly to jetted TDEs. In contrast to LSXPS J0956, these events display power law spectra, however, viscous-like interactions with the surrounding medium can induce structure in the jet. If viewed slightly off-axis, the varying optical depth could produce the quasi-thermal spectrum observed in LSXPS J0956. Alternatively, if the star’s initial orbit is sufficiently eccentric, the entirety of the debris can remain bound to the black hole. The accretion rate decays slowly before dropping rapidly as all the material is accreted, again consistent with the behaviour of LSXPS J0956. In both cases, LSXPS J0956 would be the first observed example of such a transient and I will discuss the significant questions this unique source raises for the wider TDE population.

296 Exploring the properties of TDE host galaxies

Tidal disruption events (TDEs) provide insights into the extreme environments of galactic nuclei, revealing central SMBHs and their host galaxy connection. These events are over-represented in ‘post-starburst’ galaxies, which have unusual star formation histories (SFHs), high central densities, and a position in the ‘green valley.’ Understanding how these properties influence TDE rates is key to understanding their origins. In this talk, I present the largest sample of TDE host galaxies to date, analysing 125 host galaxy SFHs using Prospector fits to UV-MIR spectral energy distributions in the context of ~650 galaxies from the GAMA survey. I will discuss key results, determine the comparative fraction of hosts with recent quenching or historical starbursts, and explore reasons for any over-representation found.

Additionally, I present a significant SMBH-bulge mass relationship for 41 TDE hosts with independent SMBH mass measurements. Restricted to SMBHs below ~1e8 M⊙, TDEs allow us to calibrate the SMBH-bulge mass relation at lower masses. This enables SMBH mass estimates using only host photometry, without the need for follow-up observations or extrapolations, invaluable given predicted detection rates for upcoming surveys. After pairing host bulge masses with SMBH masses derived from late-time optical/UV plateau emission (Mummery et al., 2023), forward modelling of TDE populations with LSST survey limits investigates observational selection effects. Results suggest a steeper SMBH-bulge mass relation may be required to span the full BH mass range, including observed TDEs. We show that this proposed relation will be testable with the future LSST TDE population, offering insight into SMBH evolution.

297 Preparing for the LSST Tidal Wave: Machine-Learned Simulated Photometry

The Vera C. Rubin Observatory’s 10-Year Legacy Survey of Space and Time (LSST) will transform time-domain astronomy, increasing the number of observed transients a hundredfold. For tidal disruption events (TDEs), this means a leap from ~100 to ~50,000, offering a unique opportunity to answer key open questions: Can we observe intermediate-mass black holes through TDEs? Why do TDEs prefer ‘green valley’ galaxies?

However, LSST’s immense data volume presents a challenge: with limited follow-up resources, we must carefully prioritize detections. To maximize LSST’s scientific impact, we must prepare now to handle this data effectively.

Using Zwicky Transient Facility (ZTF) forced photometry of all sources spatially coincident with the centre of galaxies from 2017-2023 and a combination of Gaussian processes, machine learning and SNCosmo simulations, we have developed a simulated photometric data set for LSST. What sets our approach apart is its foundation in real observational data: we leverage ZTF photometry as a base to construct a realistic LSST training set with minimal assumptions about the underlying physics of the lightcurves.

We further apply this ZTF dataset to refine target selection for the Time Domain Extragalactic Survey (TiDES), LSST’s spectroscopic follow-up program on the 4m Multi-Object Spectroscopic Telescope (4MOST). Active Galactic Nuclei (AGN) variability may lead to many false alarms in LSST, especially in the nuclei of galaxies where we hope to find TDEs. We test different cuts on the amplitude of variability in ZTF lightcurves to separate known TDEs and AGN based exclusively on their photometry to optimise follow-up resource allocation.

Forging the elements: Understanding chemical evolution and stellar populations across cosmic time

Organisers: Conor Byrne, Stephanie Monty, Ankur Upadhyaya, Louise Welsh; co organisers: Nathan Adams, Karla Arellano-Cordova, Andreea Font, Robert Izzard, Chiaki Kobayashi, Christopher Lovell, Katherine Ormerod, Vadim Rusakov, Aayush Saxena, Ragandeep Singh Sidhu, Charlotte Simmonds, Elizabeth Stanway

The origin and build-up of chemical elements in stars, dust and gas throughout the Universe is a fundamental question in modern astrophysics. Addressing this requires understanding stellar nucleosynthesis, stellar evolution and galaxy evolution across all epochs and length scales. Progress hinges on combining constraints from cutting-edge observational facilities with state-of-the-art theoretical models of stars, the Milky Way, galaxies, and the interstellar and intergalactic medium.

The advent of JWST has revolutionized studies of chemical and galactic evolution at the earliest epochs. Interpreting these observations requires advanced stellar, galactic and chemical evolution models encompassing many physical processes, including: nuclear and atomic physics, chemistry and dust formation. Combining and discussing the results from these different areas is necessary to forge a unified model of the early Universe.

One area in which models need refinement is accurately representing the conditions in the distant Universe. Observations of extreme stellar populations such as young, massive stars at low metallicity and future studies with ELT are valuable tools to bridge the gap between high- and low-redshift stellar populations. A close relationship between observations and models is essential; high-quality observations constrain models, while improved models provide better insight into early chemical and galactic evolution.

This session targets these open questions from observational and theoretical perspectives, involving stellar and galactic astronomers. Through short talks and focused discussion, we will bring together the considerable leadership and expertise of UK-based researchers in these fields, gain insight into uncertainties and limitations of data interpretation, and outline a roadmap to addressing these challenges.

298 Carbon-enhanced metal-poor stars as probes for early chemical enrichment

The oldest, most metal-poor stars in and around the Milky Way were born in pristine environments in the early Universe. Observations of local very metal-poor stars ([Fe/H] < -2.0) show that many of these stars have exceptionally high carbon abundances. These carbon-enhanced metal-poor (CEMP) stars consist of two main classes: the CEMP-no stars are thought to have been born carbon-rich, reflecting the composition of the interstellar medium enriched by the First Stars, whereas the CEMP-s stars, which are also enhanced in s-process elements and are usually found to be in binary systems, are thought to be the result of mass-transfer from a former asymptotic giant branch star companion.

Spectroscopic surveys in recent years have uncovered large numbers of CEMP stars, allowing us to begin to study them as a population. There are hints that the properties of CEMP populations vary between different Galactic environments (inner/outer halo, bulge, dwarf galaxies, globular clusters), which could point to differences in the early formation and chemical evolution of these environments. I will present an overview of what we know about CEMP populations in different environments, with a focus on the inner Milky Way — the oldest part of our Galaxy, with early conditions potentially similar to those in high-redshift galaxies.

Speaker: Anke Ardern-Arentsen (Institute of Astronomy, Cambridge)

299 Chemical Evolution Near and Far: tracing abundance patterns of C and N

Observations with JWST have opened a new window into the physical conditions, properties, and chemical abundance patterns of galaxies at high redshift. We present the chemical abundances of C, N, and O of two star-forming galaxies (SFGs) at z~5 from the Early eXtragalactic Continuum and Emission Line Science (EXCELS) survey. We compare the C and N in concert with O for these, finding elevated N/O ratios with respect to local SFGs but C/O consistent with the predictions from core-collapse supernovae yields. To understand the evolution of C/N versus O/H, we consider chemical evolutions models with variations in the initial mass function (IMF). We find that a standard or steeper IMF can explain the observed abundance ratio at z ~ 5, implying that intermediate-mass stars contribute significantly to the N production in these galaxies. Our two EXCELS galaxies pave the way for larger samples of high redshift galaxies to fully understand the chemical evolution of C/N in the early Universe.

300 Needles in Haystacks: Searching for Extremely Metal-poor Galaxies in the Local Universe

Until now, galaxy properties and chemical evolution in the lower metallicity regime have remained relatively uncharted, with considerable scatter. For example, chemical abundances like N/O ratios exhibit a scatter of 0.1–0.3 dex at an oxygen abundance of 12+log(O/H) < 7.69 (~0.1 $Z_{\odot}$), likely driven by stochastic chemical enrichment. Additionally, recent JWST observations have revealed a potentially significant increase of ionising photons produced at higher redshift than previously assumed. This new finding highlights the need for more representative samples to improve statistical constraints in this regime.

Extremely metal-poor dwarf galaxies (XMPs) in the local Universe are unique archaeological sites, preserving near-pristine gas and often regarded as the “living fossils” of the earliest galaxies. These relics serve as ideal laboratories for studying the chemical evolution and enrichment of early galaxies, while also enhancing statistical constraints in the lower metallicity regime. Furthermore, they provide a robust probe of primordial element abundances, such as Helium, offering valuable constraints on the Standard Model. However, XMPs are exceedingly rare; despite extensive searches over the past two decades, only a few hundred have been identified among millions of galaxy samples.

This talk will highlight the use of deep learning pipelines for effective identifying and characterising these galaxies in existing surveys. In our pilot study, we confirmed the metal-poor nature of 45 XMPs using strong line diagnostics. We will present these new discoveries from our ongoing search, and discuss their significance in understanding chemical evolution, ionisation states, and probing primordial helium abundance.

301 Detailed chemical composition of the globular cluster Sextans A GC-1 on the outskirts of the Local Group

Globular clusters serve as important tracers of their host galaxies' chemical evolution and star formation history. In this study, we present a comprehensive chemical abundance analysis of Sextans A GC-1, a globular cluster located in a low-surface-brightness dwarf irregular galaxy on the outskirts of the Local Group. Using integrated-light spectroscopy, we determine the cluster’s detailed chemical composition, including α-elements, iron-peak elements, and heavy elements, while also deriving its dynamical mass and mass-to-light ratio.
Our analysis reveals that GC-1 is younger and more metal-poor than typical Milky Way GCs, with a notably high dynamical mass and mass-to-light ratio. The abundance patterns indicate a complex chemical enrichment history, with α-elements exhibiting both depletion and enhancement, iron-peak elements largely at scaled-solar levels, and heavy elements showing distinct deviations from Milky Way star clusters’ trends. Particularly striking is the unusually low Mg abundance ([Mg/Fe]=−0.79 ± 0.29), a feature rarely observed in other globular clusters.
The elevated mass-to-light ratio suggests the possibility of a varying stellar initial mass function or the presence of an intermediate-mass black hole. Meanwhile, the Mg deficiency may indicate unique nucleosynthetic processes in the cluster’s formation environment. This star cluster occupies an unpopulated area in the Local Group on the age-metallicity plot with its uncommon combination of young and metal-poor nature. These findings highlight Sextans A GC-1 as an intriguing target for further studies, providing valuable insights into the formation and evolution of globular clusters in low-mass galaxies.

Speaker: Anastasia Gvozdenko (CEA, Durham University)

302 The competing effects of recent and long-term star formation histories on oxygen, nitrogen, and stellar metallicities

The fundamental metallicity relation (FMR) — the three-way trend between galaxy stellar masses, star-formation rates (SFRs) and gaseous metallicities — remains amongst the most studied extragalactic relations. Furthermore, more compact galaxies possess higher average metallicities at a given stellar mass, such that metallicity correlates particularly tightly with gravitational potential. Simulations support a shared origin for these trends relating to long-term variations in gas inflow histories; however, differences in simulated and observed galaxy samples make it unclear if this holds for real galaxies. Here, we revisit both results for star-forming galaxies, using MaNGA observations to probe galaxies’ metallicities at one effective radius. We confirm the FMR while also confirming equivalent relations for stellar metallicity (FMR) and gaseous N/O (fundamental nitrogen relation, FNR). We find that all three of these relations persist if we consider gravitational potential in place of stellar mass and/or if we consider stellar ages in place of SFR, with the gaseous relations strengthening significantly when potential is considered. The gaseous FMR disappears at high masses/potentials, while the FNR persists and the FMR strengthens significantly.

From our results, we present a unified interpretation of galaxies’ O/H, N/O, and stellar metallicities. Higher potentials are associated with higher equilibrium metallicities and earlier star-formation histories (SFHs), producing tight potential-abundance relations. SFR variations at low potential are associated with short-term SFH variations from gas inflows, mostly affecting gas abundances, while SFR variations at high potentials are instead associated with longer-term SFH variations.

303 Unraveling the Drivers of Gas-Phase Metallicity in Local Galaxies

Understanding chemical evolution in galaxies requires tracing how gas-phase metallicity evolves across cosmic time. Metallicity reflects a complex interplay between star formation, feedback, and gas flows. A key question is which galaxy properties most strongly influence metallicity. While stellar mass has long been considered the primary driver, recent studies suggest gravitational potential may be more important — yet no clear consensus has emerged.

To explore this, we perform a statistical analysis using machine learning on a large dataset combining ~5,000 galaxies from the MaNGA survey with measured dynamical masses and ~120,000 SDSS galaxies. We apply strict selection criteria to ensure high signal-to-noise emission line measurements, focusing on systems with reliable star formation diagnostics.

Using Random Forest regression and Partial Correlation Coefficients, we assess the importance of different galactic properties in determining metallicity. We also fine-tuned our machine learning model through hyperparameter optimisation to enhance the reliability of our findings. Interestingly, our results vary across the MaNGA and SDSS samples, revealing the sensitivity of outcomes to both the machine learning setup and choices made in deriving galaxy properties.

These findings highlight the challenges of isolating metallicity drivers, particularly regarding selection effects and methodological choices. While our analysis aligns with some prior results, it also reveals discrepancies, emphasising the importance of robust cross-comparisons. Ultimately, our study offers a local benchmark and a path forward: applying this framework to JWST observations will allow us to trace metallicity scaling relations across cosmic time and refine our understanding of galactic chemical enrichment.

304 Latent Space Clustering to Explore the Milky Way’s Chemical Substructure

The Milky Way’s formation history is encoded in its chemical diversity, shaped by both in-situ star formation and accretion. Using GALAH DR3, we construct a high-dimensional chemical space from 17 element abundances for 9,923 metal-poor stars. This space is then transformed into a lower-dimensional latent representation using Principal Component Analysis, capturing dominant patterns in chemical variation. We apply Extreme Deconvolution to cluster this latent space, identifying 10 chemically distinct stellar groups, including five within the dynamically defined thick disc, challenging the view of the thick disc as a single, homogeneous component.
We are currently deriving precise stellar ages for these found populations by mapping GALAH DR3 spectra to APOGEE DR17 using machine learning and applying the VAE-based age-determination method from Leung et al. (2023). Additionally, we are testing our chemical tagging framework on Milky Way analogues from the L-Galaxies semi-analytic cosmological simulation (Yates et al. 2024) to assess its ability to recover known merger histories. These efforts will refine our understanding of the thick disc’s formation and its role in the Milky Way’s evolution while validating this new chemical tagging approach.

15:35 Poster Flash Talks

15:45 Coffee Break

Advancing Space Instrumentation and Low-Cost Mission Concepts

Organisers: Adam Amara, Steve Eckersley, Lucia Fonseca de la Bella, Hamish Reid; co organisers: Malcolm Dunlop, Oscar Gonzalez, David Hall, Beatriz Sanchez-Cano

The rapid evolution of space instrumentation and mission design is ushering in a transformative era for solar-terrestrial physics, planetary science, and astrophysics. With an increasing emphasis on affordability and innovation, the space science community is exploring cutting-edge technologies and low-cost mission concepts that promise groundbreaking scientific discoveries. Recent initiatives by the European Space Agency (ESA)—including the M7/F2 program, the forthcoming M8 and F3 calls, and the agile mini-Fast mission concepts—highlight the growing demand for advanced instrumentation and creative mission architectures. In parallel, the UK Space Agency (UKSA) is driving technological progress through its Enabling Technology Programme and bilateral Science and Exploration Programme, fostering international collaboration and the development of next-generation space science missions.

This session invites contributions from researchers, engineers, and mission teams engaged in the design and development of innovative instrumentation and low-cost missions. We particularly welcome discussions on instruments targeting solar-terrestrial physics, extrasolar astrophysics, and planetary exploration, as well as proposals for small satellite missions and other cost-effective approaches. This session provides a unique platform for Principal Investigators (PIs) to lead the charge on these transformative missions. By bringing together expertise from academia, industry, and space agencies, this session seeks to highlight the UK’s pivotal role in shaping the future of space science. Attendees will explore how technological advancements, strategic collaborations, and resourceful mission planning can deliver high-impact scientific outcomes. Together, we can unlock the full potential of low-cost space science and exploration missions.

305 The ESA Comet Interceptor mission

ESA's Comet Interceptor will launch to the Sun-Earth L2 point in 2029, where it will be 'parked' in a stable L2 halo orbit for a period of up to 2-3 years, until a suitable opportunity for a flyby mission to an Oort Cloud comet presents itself. Shortly before the flyby, the main spacecraft will deploy 2 small probes (one provided by JAXA, one by ESA) allowing multiple paths through the coma and past the nucleus to be sampled. This will give a 3D snapshot of the comet at the time of the flyby, testing spatial inhomogeneity in the coma and interaction with the solar wind on all scales. This will be a unique measurement that was not possible with Rosetta, in addition to the fact that we will target a new class of comet (a much less evolved body), which will allow interesting comparisons to be made with the results from 67P. The spacecraft will have a high resolution camera to take images at up to 10m/pix resolution, a mass spectrometer based on Rosetta/ROSINA heritage, an infrared remote sensing camera/spectrograph, including the first thermal infrared camera sent to a comet, a package of dust, fields and plasma sensors, and, on the small probes, additional UV and visible cameras, including an all-sky scanning polarimeter to reveal dust properties.

306 The ARRAKIHS mission

The ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) has been selected for the European Space Agency (ESA)’s second fast (F-2) space mission, planned launch in 2030. The ARRAKIHS mission aims to study the nature of dark matter, arguably the biggest mystery in astronomy and cosmology, by observing the low-surface brightness features around a large number of external galaxies similar in size to our Galaxy, the Milky Way. After a trade-off study, Teledyne e2v (Te2v)’s CIS304 CMOS detector has been chosen for the baseline visible (VIS) detectors. The ARRAKIHS mission will be the first high-precision optical astronomy mission to utilise a low-noise CMOS imager, instead of the traditional CCDs. Mullard Space Science Laboratory, UCL is leading the characterization work for this new CMOS detector manufactured by Te2v, a UK-based company. We summarise the mission concept of ARRAKIHS and report the development of our detector characterisation work in collaboration with Te2v and ESA.

307 CosmoCube: Probing the Cosmic Dark Ages with a Miniature Radiometer in Lunar Orbit

The “Dark Ages” of the Universe, spanning redshifts z ~ 30–250, remain one of the last unexplored frontiers in observational cosmology. This pre-stellar epoch, rich in neutral hydrogen, offers a pristine view into the formation of structure, the properties of dark matter, and early cosmic evolution. The redshifted 21-cm hyperfine transition from this period encodes a wealth of information, but is inaccessible to ground-based instruments due to ionospheric distortion and pervasive radio frequency interference (RFI) below ~45 MHz.

CosmoCube is a UK-led space mission concept designed to overcome these limitations. It proposes a precision-calibrated, low-power radio radiometer operating from a low-cost satellite platform in lunar orbit. The spacecraft will conduct deep, RFI-free observations from the Moon’s far side, enabling detection of the sky-averaged 21-cm signal across 5–100 MHz (corresponding to z ~ 13–285).

The mission integrates heritage from the REACH experiment with novel hardware developments, including a deployable wideband antenna, a compact RFSoC-based spectrometer, and a thermal-stable calibration system. Data will be analysed using advanced Bayesian pipelines to isolate the cosmological signal from strong astrophysical foregrounds.

CosmoCube offers a timely and cost-effective opportunity to deliver the first direct constraints on the Dark Ages, with potential implications for the Hubble tension, dark matter-baryon interactions, and the physics of the early Universe. We present the mission architecture, science goals, instrumentation status, and the roadmap to flight in the current decade.

308 1. SuperASTRO: an innovative super-spectral small satellite for advanced low-cost astronomy

Space-based astronomy offers a unique opportunity to observe the celestial sphere, free from atmospheric distortions and absorptions, with the potential for almost continuous, uninterrupted observations. Traditionally, space-based telescopes have been developed and operated by large space agencies and institutions, resulting in very expensive missions with long development times. However, recent small satellite missions, like HaloSat, have demonstrated the potential to provide valuable astronomical data at a lower cost and with shorter development cycles. SuperASTRO is a novel small satellite concept equipped with a super-spectral imager developed by Surrey Satellite Technology Limited (SSTL) in collaboration with academic advisors from the University of Surrey. With the expected end of life and planned launches of current space astronomy missions, spectral bands between the wavelengths of 0.3 and 0.5 microns are anticipated to be uncovered by any other space telescope. The SuperASTRO imager is designed to be equipped with up to 66 filters covering spectral bands ranging from 0.3μm to 0.96μm to fill this gap in observations while showcasing the capabilities of small satellites in delivering valuable astronomical data. Additionally, the development of small satellites using SSTL's vertically integrated approach presents significant advantages in terms of cost and development time providing at the same time greater operational flexibility. This presentation will provide an overview of an internal study on potential small-satellite astronomy missions, which led to the development of SuperASTRO. It will highlight the innovations behind this concept and evaluate its feasibility, demonstrating its great potential for application in both institutional and commercial astronomy.

309 ROARS: Revealing Orbital and Atmospheric Responses to Solar activity

The Earth’s upper atmosphere highly sensitive to solar activity and the solar wind-magnetosphere interaction. Magnetospheric current systems close through the ionosphere and associated ion-neutral collisions, i.e. Joule heating, together can drastically modulate the spatially- and temporally-varying outer extent of the atmosphere. Unlike the many isolated in-situ measurements carried out by space missions so far, distributed neutral, plasma and magnetic field observations by a tetrahedron of micro-satellites, in tandem with precise tracking of the satellites’ orbital dynamics, offer the global view necessary to disentangle the complex transfers of energy and momentum through the tightly coupled magnetosphere-ionosphere-thermosphere system.

In this talk we outline a candidate mission architecture for the new ESA mini-Fast programme. This novel mission architecture seeks to obtain the first coordinated magnetic field, plasma and neutral measurements across a range of altitudes, latitudes and longitudes to resolve and characterise the energy entering the upper atmosphere, the pathways through which this is redistributed, and the coupling back to the geospace environment. A comprehensive ground segment will simultaneously relate information on the D- and E-region dynamics to the in-situ measurements.

In addition, we outline two enabling technology development studies relating to a fibre-coupled quantum diamond magnetometer for precise gradiometer measurements and a quantum-limited levitated nano-particle instrument for absolute measurements of the neutral atmosphere, which promise to enhance future mission concepts in this area and beyond.

310 UK-ODESSI: A Low-Cost, Low-Earth Orbit, In-Orbit Pathfinder for UK Space Weather Instrumentation

Observations are critical to implementing timely strategies for mitigating potentially damaging space weather effects. The UK has an extensive heritage in developing and deploying scientific instrumentation to study space weather phenomena, on which basis a plethora of novel developments in space-borne space weather instrumentation are currently underway in UK academic, government and industrial establishments. In order to capitalize on these innovative developments - while exploiting the potential of the new generation of small-form UK satellites to provide high-quality data at a lower cost in low-Earth Orbit (LEO) and potentially beyond - we propose a national in-orbit pathfinder mission. UK-ODESSI (UK-Orbital pathfinDEr for Space-borne, Space-weather Instrumentation) will host a suite of emergent UK-led space weather instrumentation on a low-cost small-sat platform based on existing UK heritage, located in a sun-synchronous terminator LEO at some 500-600 km altitude above Earth. Such an orbit - achievable via, for example, either a low-cost Space-X rideshare or even a dedicated UK launch - would not only provide continuous real operational data (except during short eclipse periods at one solstice) but would also act as a test bed for space weather instruments as well as satellite/ground-segment sub-systems/technologies being developed in parallel in the UK. UK-ODESSI, which would target a launch time-scale and cost envelope similar to those of an ESA mini-F-class mission, would enable the development and testing of potential new space weather service capabilities by providing additional and novel inputs for nowcast and forecast models and climatology.

311 VERVE - a proposal for an ESA mini-Fast mission to Venus

Ground-based observations are starting to uncover reduced gases that are very unexpected in the oxidised atmosphere of Venus. Their presence suggests a redox disequilibrium, with one possible contributor being the presence of anaerobic micro-organisms. We are proposing a mission to the ESA mini-Fast call to study these gases up close, hoping for a ride to Venus alongside ESA EnVision in 2031. I will discuss the plan for VERVE - the Venus Explorer for Reduced Gases in the Environment - including its instrument and science plan, and the relation to other missions including the Venus Morning Star life-seeking mission.

312 LIRIS – A small satellite concept to provide high resolution maps of water on the Moon.

The detection of possible widespread surficial H2O/OH on sunlight and shadowed regions of the lunar surface was one of the most unexpected discoveries of the 2000’s. Remote sensing measurements of the H2O/OH absorption 3 µm feature from data sets from e.g. the Moon Mineralogy Mapper (M3) on the Chandrayan-1 spacecraft in 2009 gave an indication of possible spatial and time of variations in surficial water concentration. The identification of water and determining its abundance at scales <75 m will provide critical new knowledge on a possible “lunar water cycle” and support future human and robotic exploration. With advancements in technology, improved lunar infrastructure (including services such as ESA’s Moonlight) and increased accessibility enabled by lower cost rideshares now allow for a fast (e.g. <4 year), focused mission to answer this question is now possible.

The LIRIS small satellite concept builds on experience from the Lunar Pathfinder development at SSTL towards designing a variant of the Carb+ platform series tailored for the lunar environment. Building on heritage from the DarkCarb imager flown in 2023, the multispectral imager will be capable of providing sub-meter resolution images of the lunar surface in spectral bands around 3 microns. The spacecraft will host a thermal infrared imager, capable of imaging in the 6-25 microns range, which is an evolution of the University of Oxford’s Lunar Thermal Mapper to provide thermal context for environment and surface composition characterisation.

This presentation will describe the details of the concept and science case, as well as the current status.

Solar Physics, Stellar Physics, and Exoplanetary joint session: bridging the gap

Organisers: David Brown, Malcolm Druett, Alex Pietrow, Don Pollacco, Angela Santos, Thomas Wilson

Understanding the formation, evolution, and behavior of our own Star and Solar System in a Stellar or Galactic context requires deeper coordination between solar and solar system investigations and the characterisation of stars and planets across the Milky Way.

The objectives of this session are:
(1) To bridge the gap between the stellar and solar communities, and between the exoplanet and stellar communities by bringing together experts to discuss the latest results in these fields.
(2) To provide a platform for collaborations and dissemination channels between the solar, stellar, planetary and exoplanetary communities.
(3) To provide an update about the PLATO mission (ESA’s next medium-class mission, which will continuously observe over 200,000 FGKM-dwarf stars with high cadence and quality for at least 2 years) and discuss its stellar and planetary characterisation potential.

We particularly encourage applications with relevance to the Sun-as-a-star, discoveries in Stellar physics with relevance to the Sun, advances in exoplanet discovery and characterisation, and Extreme space weather events and habitability such as:

Spatially resolved or Sun-as-a-star observations and models giving insight into mechanisms responsible for signatures in unresolved observations of stars, for example longer-term variations, flares, and other activity, and feature locations on the stellar disk.
Space weather observations and models with applications to understanding the environments and conditions around stars.

The latest findings regarding solar-type stars, including physical modelling, and stellar populations and the insights these can provide regarding behaviours that may occur on our local star and surrounding planetary environments.

Recent observations and modeling related to the spatially resolved images of nearby supergiants. How can the future of spatially resolved stellar observations help us to better understand the Sun?
Transit, radial velocity, and astrometry discovery and characterisation of terrestrial exoplanets particularly related to understanding the formation and evolution of these bodies.

Works related to the preparation and prospects for PLATO With the launch of PLATO in late 2026, this discussion is timely to highlight advances in the mission and galvanise the UK community to take full advantage of the data.

16:15 Prep time

313 Disentangling stellar and planetary signatures at high resolution

Almost everything we know about exoplanets comes from light originating from their far more luminous host stars. As a consequence, signatures from stellar surface inhomogeneities can imprint themselves on exoplanet observations; this is especially prevalent at high spectral resolution where even subtle signatures can be decomposed. For Sun-like stars, such inhomogeneities are primarily driven by heat transport via convection at the surface interplaying with magnetic fields, giving rise to various phenomena from granulation and oscillations to faculae/plage, spots, and flares etc. In this talk, I will show how these phenomena alter the shape and position of the stellar absorption lines that we use to probe exoplanet characteristics. The impact is far-reaching, from exoplanet mass determination to our analysis of star-planet dynamical histories to teasing out the chemical makeup of exoplanet atmospheres. I will also discuss ongoing efforts to use high spectral resolution to unveil stellar variability fingerprints and disentangle underlying exoplanet signatures

314 An ultracool bridge to exoplanet magnetic fields

Magnetic fields play a key role throughout the lives of planets, shaping their formation and atmospheric escape. At planetary scales, magnetism is driven by the motion of electrically conductive material in their interiors. Therefore, magnetic fields are a unique probe of a planet's interior structure. In our solar system, planetary magnetic fields are signposted by their bright radio emission, driven by electrons trapped within the magnetic field. Despite extensive searches, radio emission from an exoplanet has so far eluded detection. As a result, our understanding of magnetism on extrasolar planets is in its infancy. However, Jupiter-like objects known as ultracool dwarfs (UCDs) have been detected at radio wavelengths for over two decades. These objects, comprised of late M dwarfs and brown dwarfs, share many structural similarities to Jupiter, and are ideal targets for advancing our understanding of magnetic fields on Jupiter-like exoplanets. However, this potential has not been fully realised, primarily due to a lack of numerical models to interpret their radio emission. In this talk, I will present our recent progress on inferring the magnetic characteristics of UCDs via their radio emission from a numerical perspective. Ultimately, this work will enable robust estimates for the magnetic fields of extrasolar planets in anticipation of their direct detection with upcoming radio facilities such as LOFAR 2.0 and the SKA.

315 Tackling Supergranulation in Earth-Twin Surveys using the HARPS-N Solar Data

In recent years supergranulation has emerged as one of the biggest challenges for the detection of Earth-twins in radial velocity (RV) planet searches. Supergranulation introduces RV variations on timescales of 1-2 days with amplitudes of 0.5-1 m/s, considerably larger than the expected 10 cm/s signal from Earth-like planets. I will present new work focused on mitigating the impact of supergranulation using Gaussian Processes in the time domain. I will apply this new method to HARPS-N solar data sets, and show how this method has led to the discovery of a ‘supergranulation cycle’, in phase with the activity cycle of the Sun. I will also discuss observational strategies that can be employed to characterise supergranulation in other stars, a critical step in the search for Earth-twins. Finally, I will show that by modelling the supergranulation signal in this way, we can improve the detection of planets with smaller RV signals, bringing us closer to identifying Earth-like exoplanets.

316 Revealing PLATO’s planet discovery potential across stellar types

The ESA PLATO mission will be launched by the end of 2026 with the goal to detect terrestrial planets in habitable zones of bright, Solar-like stars. Our study assesses PLATO’s capability to discover transiting planets by computing its detection sensitivities. We analyse how these PLATO detection sensitivities vary across F, G, and K-type stars and evaluate the effectiveness of different observing strategies. Specifically, we compare the impact of longer observations in the southern hemisphere versus transitioning to the northern field to determine which approach maximizes PLATO’s sensitivity to detect a true Sun-Earth analogue.
In addition to estimating PLATO’s sensitivities, we compute these values for other photometric missions, mainly TESS. Comparing the sensitivities between the two missions allows us to highlight the discovery space that was not covered by TESS but will be by PLATO.
As photometric data for the Northern and Southern PLATO field exists from other missions, we make use of this existing photometry which enhances our sensitivity estimates. In the Southern hemisphere we leverage TESS observations, while in the North we integrate data from both TESS and Kepler. Although PLATO has a higher precision than TESS, when including this archival data, especially from the continuous viewing zone where more than 3 years of TESS data are available, PLATO’s detection sensitivities are enhanced.
Our results provide insights into PLATO’s planet discovery potential and the observing strategy that will have the highest sensitivity to Earth-like planets in the habitable zone of their Sun-like stars.

317 Investigating Star-Planet Compositional Ties for Systems with Host Stars of Varying Composition

As stars and planets are formed in the same environment, it is conceivable that a fundamental connection exists between the compositions of planets and their host stars. Exploring this relationship offers insights into the intricate history of the systems' formation and evolution. I investigate both the existence and complexity of a systematic relationship between the compositions of host stars and their planets. To unravel such complexities, a diverse stellar sample that spans a wide range of chemical balances is needed. I put emphasis on [α/Fe] variety, as these α-elements are present in the interiors of rocky exoplanets. Planets orbiting iron-poor stars are thus of particular interest, offering an opportunity to study stars with compositions like and unlike the Sun; by leveraging planetary interior modelling, I analyse how the elemental abundances of these stars relate to the inferred compositions of their orbiting small planets. Here, I present results from the analysis of an extensive and homogenous sample. Understanding these trends is crucial for refining models of planet formation and assessing the diversity of planetary systems beyond our own.

318 Small exoplanets and their host stars: from Kepler and TESS to PLATO

During the past years there has been a major paradigm shift in exoplanet science, due to the realisation that small planets come in two distinct flavours, i.e., super-Earth and sub-Neptune planets, separated by a radius valley where planets are rare. I present the latest research from statistical studies of small transiting Kepler and TESS planets. In particular, I show how the location of the radius valley is observed to depend on stellar parameters including their age (Ho & Van Eylen 2023). I highlight the challenges in observing the valley for low mass M-type stars (e.g., Ho et al. 2024). I furthermore discuss the latest insights in studying the compositions of small rocky planets, including an exciting link between rocky planet compositions and stellar ages (Weeks, Van Eylen, et al., 2025, accepted), and I discuss how our solar system planets fit within this broader galactic context. Finally, I highlight how all of this progress has crucially relied on precise and homogeneous stellar characterisation, and show how PLATO can be expected to address several of the main open questions that remain.

Speaker: Vincent Van Eylen (UCL)

Barred Galaxies: Unravelling Their Evolution, Dynamics and Cosmic Role

Organiser: Zoe Le Conte; co organisers: Alex Merrow, Rebecca Smethurst, Thomas Tomlinson

Our understanding of bar formation, evolution, and their interactions with host galaxies is rapidly advancing, revealing new insights into their role in galaxy evolution. Bars are among the most common features in disc galaxies, present in over two-thirds of local spirals, and they influence their hosts by redistributing angular momentum, triggering gas inflows that fuel star formation and potentially feed AGN. Bars also reshape stellar orbits within the galaxy, including the inner regions, outer discs, and stellar halos.

Recent observations from high-resolution surveys like the HST and JWST have provided unprecedented insights into bar-driven evolution across environments and redshifts. Integral field units such as MUSE offer critical data on stellar populations, stellar and gas kinematics, bar-driven star formation and AGN activity, while Gaia enables a star-by-star analysis in the Milky Way.

Simulations complement these advances by modelling barred galaxies with increasing resolution, allowing for detailed studies from high redshifts to the present. These simulations help interpret observational data and improve understanding of stellar chemical evolution and accretion processes, thus facilitating a more accurate interpretation of observational data.

This session will address the still outstanding questions about bar formation, environmental influences on galaxy stability, the kinematics of bars, the role of bars in triggering and fuelling AGN, and bar-driven evolution within dark matter halos. We will discuss how combining high-resolution photometric surveys with cosmological simulations can bridge theory and observations, and how upcoming facilities like MOONS, BlueMUSE, MAVIS, SKA, and ELT will enhance our understanding of galaxy dynamics.

319 Bar-driven fuelling of AGN

Despite most supermassive black hole (SMBH) growth occurring via merger-free processes, the underlying mechanisms driving this secular evolution are poorly understood. We investigate the role that both strong and weak large-scale galactic bars play in mediating this growth, by analysing the active galactic nucleus (AGN) fraction in strongly barred, weakly barred, and unbarred galaxies up to z = 0.1, with a median z=0.067. We find an optically selected AGN fraction of 31.6 ± 0.9 % in strongly barred galaxies, 23.3 ± 0.8 % in weakly barred galaxies, and 14.2 ± 0.6 % in unbarred disc galaxies. These are highly statistically robust results, strengthening the tantalising findings in earlier works. Strongly barred galaxies have a higher fraction of AGN than weakly barred galaxies, which in turn have a higher fraction than unbarred galaxies. Thus, while bars are not required in order to grow an SMBH in a disc galaxy, large-scale galactic bars appear to facilitate AGN fuelling, and the presence of a strong bar makes a disc galaxy more than twice as likely to host an AGN than an unbarred galaxy at all galaxy stellar masses and colours. With this robust correlation now demonstrated, we can look at the complex interplay between AGN, bars, and galactic bulges. Since bulges can be grown via the inflow of gas driven by bars, and a number of scaling relationships demonstrate a correlation between AGN and bulges, disentangling these processes will illuminate secular fuelling, furthering our understanding of galaxy evolution as a whole.

Speaker: Dr Izzy Garland (Masaryk University)

320 Decoding imprints of bars and AGN in the AMR of the Auriga galaxies.

The age-metallicity relation (AMR) is a key observational tool for understanding the chemical evolution and formation of galactic discs over time. Using the Auriga cosmological simulations—a suite of high-resolution Milky Way-like galaxy models—we analyze the AMR across the full simulation suite. We have found anomalous AMR features in certain galaxies, which trace past dynamical events such as Active Galactic Nuclei (AGN) activity and bar formation. We divided the thin and thick discs into inner and outer regions to examine how these events differentially influence galactic structure, star formation history, and chemical evolution. Our results demonstrate the AMR’s unique ability to decode a galaxy’s evolutionary history, particularly in revealing how internal processes like bars and AGN shape disc galaxies.

321 What makes the bar go round: Drivers of bar pattern speed in cosmological simulations.

Galactic bars rotate at different rates, both in the observed Universe and in simulations, but the precise reasons for these various pattern speeds are not fully understood. We use a high temporal resolution version of the Auriga suite of magneto-hydrodynamical cosmological zoom-in simulations to identify the galaxy properties and histories that set the pattern speeds of bars. In contrast with generally expected evolution, we find that the bars in these simulations do not typically slow down from formation to z = 0, instead preferentially speeding up. This implies that dynamical friction from the dark matter halo does not dominate the evolution of these bars. We find that the faster bars are those which are stronger, older, and hosted in more massive, baryon-dominated galaxies. Galaxy interactions have a secondary effect on pre-existing bars, typically accelerating their rotation, but we find no systematic difference between the pattern speeds of bars formed by interactions when compared to those formed in isolation.

322 Swooping in on the drivers of the spin-age relation using barred galaxies from COLIBRE

Observations from the SAMI integral field spectroscopic survey have demonstrated that older galaxies have lower spin and younger galaxies have higher spin, even when the effects of stellar mass and environment are controlled. A possible driver of this “spin-age” relation is the presence of internal secular heating driven by bars and spiral arms. In the next-generation EAGLE simulation, COLIBRE, we find a population of high-spin, flattened galaxies and evaluate the origin of the spin-age relation in this new cosmological, hydrodynamical simulation. We investigate the cosmic role of barred galaxies, using the model to explore how these systems move through this parameter space and evolve over time. This presentation will demonstrate the emergence of a realistic spin-age relation in COLIBRE, explore the role of bars in driving this relation, and make comparison to the same observation relation in the SAMI survey using the open source, mock IFU software, SimSpin.

323 Bars in TNG50 - slowdown and formation of double bars

Bars are common structures in spiral galaxies, and until recently, their formation and evolution were primarily studied through numerical simulations of individual galaxies and theoretical models. Over the past decade, however, hydrodynamical cosmological simulations, which model a wide range of physical processes involved in galaxy evolution, have opened new avenues for investigating bar dynamics, producing populations of simulated bars. In my talk I will present our analysis of the TNG50 simulation from the IllustrisTNG suite, focusing on two key aspects of bar evolution.

One critical parameter in bar evolution is its pattern speed. Previous studies have shown that the pattern speed tends to decrease over time due to dynamical friction exerted by dark matter halos, although gas inflows can counter this slowdown by contributing to the angular momentum balance. I will discuss how these and other factors influence the evolution of bar pattern speed in TNG50.

Up to 1/3 of bars observed in the Local Universe appear to double-barred, i.e. host an inner bar within the bigger outer one. In the second part of my talk I will present our new scenario of the formation of double bars, that is demonstrated through the two examples of these objects found in TNG50.

Speaker: Dr Marcin Semczuk (Universitat de Barcelona)

324 The stellar bar - dark matter halo connection in cosmological simulations

Stellar bars in disc galaxies grow as stars in near circular orbits lose angular momentum to their environments, including their Dark Matter (DM) halo, and transform into elongated bar orbits. This angular momentum exchange during galaxy evolution hints at a connection between bar properties, the DM angular momentum, specific angular momentum and halo spin λ, the dimensionless form of DM angular momentum. We investigate the connection between multiple DM halo properties and galaxy properties in the presence/absence of stellar bars, using the cosmological zoomed-in Auriga and Superstars simulations of Milky Way mass galaxies. We determine the bar strength (or bar amplitude, A2/A0), using Fourier decomposition of the face-on stellar density distribution. We determine the halo spin for barred and unbarred galaxies (0 < A2/A0 < 0.7) in the centre of the DM halo, close to the galaxy’s stellar disc. Previous studies using a large sample of disc galaxies from the magneto-hydrodynamic TNG50 simulations have shown an anti-correlation between halo spin and bar strength at redshift z=0, predicting a large population of barred galaxies to be found in lower spinning DM halos. To understand the role of stellar bars in transferring angular momentum from the disc to the DM halo we undertake further detailed investigation using high-resolution Auriga simulations, which follow the same galaxy formation model as the Illustris suite. I will present our findings from the Auriga simulations and compare them with previous results from the TNG50 simulations.

Galactic Foregrounds at Low Frequencies and CMB Cosmology: Current Challenges and Opportunities

Organiser: Patrick Leahy; co organisers: Clive Dickinson, Vasundhara Shaw

Galactic foreground emissions in the Milky Way below a few 10s of GHz are dominated by three mechanisms: synchrotron radiation from cosmic ray electrons interacting with magnetic fields, free-free emission from electron-ion interactions, and anomalous microwave emission (AME) from rotating dust grains. These emissions are observed through Stokes parameters: I (total intensity), Q and U (linear polarization). Large-scale polarized emission primarily comes from Galactic synchrotron emission and thermal dust at higher frequencies.

Understanding these foregrounds is critical for decoding Galactic magnetic field structures governing Galactic dynamics and ultra-high energy cosmic ray propagation, while being fundamental for CMB cosmology research, particularly in detecting B-modes and analyzing 21-cm cosmological signals.

Recent multi-band radio surveys have revolutionized our approach through key initiatives like C-Band All-Sky Survey (C-BASS) at 5 GHz, QUIJOTE Wide Survey (11-20 GHz), Simons Observatory (27-280 GHz), and the upcoming LiteBIRD satellite mission (40-400 GHz). These observations enable comprehensive examination of Galactic foregrounds across frequencies, advancing both CMB foreground separation and our understanding of Galactic magnetic fields.

This research field exemplifies the convergence of observational capabilities and theoretical advances, fostering collaboration between CMB cosmology, 21 cm intensity mapping, and ISM physics communities. This session will feature keynote presentations on survey status, Galactic magnetic field physics, and radio foregrounds' impact on CMB science. Subsequent focused presentations and poster sessions will showcase ongoing research, followed by structured group discussions. The hybrid format ensures global participation through focused presentations, poster sessions, and structured group discussions, reflecting the field's international significance.

16:15 Prep time

325 The C-Band All-Sky Northern Survey (C-BASS N)

We present results from the C-BASS Northern survey. The survey covers the whole northern sky above declination -15.6 degrees with data taken in both total intensity and linear polarization at 4.76 GHz and with an angular resolution of 44 arcmin. The primary aims of C-BASS are to support CMB studies by improving our understanding of contaminating foreground emission, especially in polarization, and to study the radio emission of the Galaxy. Here we present the northern maps and derived data products. We will discuss the polarized spectral index distributions measured using C-BASS N data in combination with WMAP and Planck, and their implications for measurements of the CMB B-mode polarization. We will also highlight results from papers accompanying the up-coming data release which present analysis of the absolute intensity background, morphology of the polarized structures, spatial power spectra of the polarized synchrotron foregrounds and results on Faraday rotation in the interstellar medium.

326 QUIJOTE views of our Galaxy

QUIJOTE (Q-U-I JOint TEnerife) is a pair of 2.25m telescopes observing from Teide Observatory, Tenerife, at 10-20GHz (Multi-Frequency Instrument, MFI) and 30 and 40GHz (Thirty and Forty Gigahertz Instrument, TFGI). The wide survey of MFI1 has recently been released, while TFGI and MFI2 observations continue, and a 90GHz camera is under development for the future.

I will summarise the current data release of MFI and the key results obtained with it so far, in particular the wide survey of our Galaxy and studies of various Galactic regions. I will also briefly describe ongoing and upcoming observational experiments at Tenerife, including GroundBIRD, LSPE-STRIP, and TMS, which combined with QUIJOTE will give observations of the northern hemisphere at degree scale throughout 10-220GHz, an unprecedented range of frequencies from a single observing site.

327 The LiteBIRD space mission and the Galactic foreground challenge

LiteBIRD (the Lite (Light) spacecraft for the study of B-mode polarization and Inflation from cosmic background Radiation Detection) is a space-based mission dedicated to primordial cosmology. Its objective is to investigate cosmic inflation by targeting primordial B modes in the CMB polarization. Specifically, it will focus on both the reionization and recombination peaks to measure the tensor-to-scalar ratio. To achieve this, LiteBIRD will map the polarization of microwave emissions across the entire sky over a wide frequency range. In this talk, I will introduce the mission and discuss the primary data analysis challenge we must overcome to extract the cosmological information: mitigating Galactic foreground contamination across a large sky fraction. This requires developing novel component separation techniques that can effectively handle the complexity of foreground emissions, their spatial variations in frequency scaling, and the uncertainties in our current knowledge of them. By addressing this challenge, LiteBIRD will also produce state-of-the-art full-sky maps of polarized foreground emissions, particularly thermal dust and synchrotron radiation.

328 The Simons Observatory: constraining primordial B-modes

The Simons Observatory Small Aperture Telescopes (SATs), located in Chile’s Atacama desert, are currently observing the polarised microwave sky at degree scales, on a quest to measure or constrain primordial gravitational waves, or B-modes, from the very early Universe. Disentangling this elusive signal from Galactic foregrounds, instrumental noise, and systematic effects requires robust pipelines tackling tasks that range from data reduction to component separation. In this talk, I will focus on the SAT power spectrum pipeline - selected to obtain the first constraints on the tensor-to-scalar ratio r - and explain strategies to minimise its bias and uncertainty in the presence of polarised synchrotron and dust emission from the Milky Way.

329 The C-Band All-Sky Survey (C-BASS): Diffuse Component Separation of the Temperature Sky

Accurate separation of diffuse foreground components in temperature maps is crucial for cosmological and astrophysical studies. We use the Commander code, which employs a Bayesian approach through Gibbs sampling, to perform a new decomposition of low-frequency foregrounds. This analysis builds upon the methodology used in Planck 2015, incorporating 31 maps, enabling a cleaner separation of synchrotron, free-free, and spinning dust emissions. Our main products are a new full-sky synchrotron spectral index map, an improved spinning dust amplitude map at 22.8 GHz based on a lognormal phenomenological model—showing a stronger correlation with the thermal dust map than in previous studies—and a completely new full-sky map at 4.76 GHz, which provides a significantly improved tracing of synchrotron emission. This refined analysis enhances our understanding of foreground emissions and is a valuable resource for future cosmological and galactic research.

Speaker: Gabriel Amancio Hoerning (The University of Manchester)

Intracluster light: illuminating the next generation of galaxy cluster science

Organisers: Jessica Doppel, Stephane Werner, Mathilde Jauzac

In the era of next-generation telescopes such as JWST and Euclid, high-resolution, visible-by-eye images of the diffuse intracluster light (ICL) of galaxy clusters are becoming increasingly abundant. This component of galaxy clusters is comprised of stars, including star clusters, stellar remnants, gas, and dust that do not belong to the individual cluster galaxies, but rather to the overall cluster itself. The ICL has been positioned as an extremely valuable tool for understanding many properties of galaxy clusters, e.g. their dynamics, accretion histories, and shapes. Indeed, the existence of ICL itself provides a testing ground for the hierarchical formation scenario predicted by our current cosmological paradigm. By tracing the assembly history of galaxy clusters, ICL components serve as tracers of galaxy cluster dynamics. It can thus be used to trace their dark matter distribution of clusters and act as a new dark matter probe.

Combining the incoming wealth of ICL observations and the push towards higher resolution galaxy cluster simulations has the potential to lead the field not only towards a more detailed understanding of our current datasets but also towards answering still-open and key questions: How do we quantify ICL? What is the best way to measure ICL? How does ICL evolve with time? How can ICL be used to probe dark matter? We aim for this session to address these open questions and identify scientific gaps in this emerging research field.

330 Multiwavelength views on the mass distribution of galaxy clusters

Multiwavelength data on the most observed galaxy clusters allows for comprehensive mass modelling of each component: dark matter, intra-cluster gas, the galaxy's baryons, and the intra-cluster stars. Such modelling could be done with a combination of multiple mass probes, constraining the total mass of each individual baryonic component, but no method for such modelling has been released.
Recent studies have shown that it was possible to make a self-consistent mass distribution model separating the intra-cluster gas from the rest of the mass to benefit from X-ray constraints (Beauchesne et al., 2024). The first JWST observations demonstrated its ability to map the intra-cluster light in a fraction of the observing time previously required and allowed its inclusion into galaxy cluster mass models with an approach similar to the X-ray gas.
I will present a modified version of the method presented in Beauchesne et al. (2024), where we include a new mass component to reproduce the ICL. We extend the set of observables by adding direct constraints on the velocity dispersions for the cluster member and the ICL. The produced models can be split into each main cluster component, and each baryon component is fitted on specific observables jointly with the lensing. I will present the early results obtained on the cluster test case, Abell S1063. I will compare the stellar-mass-to-light ratio from the favoured mass model to its estimation with spectral energy density fit. In the case of Abell S1063, we found a relative agreement between those two probes.

331 First look into the shapes of ICL with Euclid Q1

Galaxy clusters form through hierarchical merging, with the intracluster light (ICL) serving as a luminous tracer of these processes. The distribution and morphology of ICL provide critical insights into the evolution of galaxy clusters. Moreover, the stripped stars that form the ICL are bound to underlying gravitational potential of the cluster, thus making the ICL a valuable probe for the dark matter distribution. Additionally, the shape and radial extent of ICL can be used to study a cluster’s dynamical state, helping to determine whether it is relaxed or merging. However, the faint nature of ICL poses significant challenges for studying its characteristics. With the advent of high-resolution data from Euclid, we can now study the ICL's shape and extent with unprecedented depth. Using data from the Euclid Q1 release, we present a pilot study of the ICL shapes (e.g., ellipticity, position angle and lopsidedness) across multiple wavelengths in ~20 massive eRosita galaxy clusters. We assess which Euclid filter—VIS, H, J, or Y—is the most effective for measuring the ICL’s shape and radial extent, and investigate the link between ICL morphology and the dynamical state of the clusters. Additionally, we highlight the need for optimised data processing techniques tailored to the low surface brightness regime, which are essential for accurately constraining the ICL’s properties and deepening our understanding of galaxy cluster evolution. This work lays the foundation for extending the analysis to the upcoming Euclid DR1 which will offer a larger statistical sample for more robust investigations.

332 Energetics of the intracluster stars and dark matter

The diffuse stellar component of galaxy clusters known as intracluster light (ICL) has been proposed as an observable tracer of the cluster’s dark matter (DM) halo. Investigating the energetics of the intracluster stars is essential for understanding how they are linked to the underlying DM distribution and, consequently, assessing the reliability of the ICL as a DM tracer. In this talk, I will outline how the orbital properties of the intracluster stars differ from both the DM and galaxy population, and propose a possible mechanism to explain these differences.

Speaker: Joseph Butler (University of Nottingham)

333 The dawn of intracluster light in proto-clusters

Intracluster light (ICL) appears in observations as a faint, diffuse glow at the heart of galaxy clusters, composed primarily of stars that drift freely within the cluster's gravitational potential, untethered to any galaxy. To unravel the story of its early formation, we must journey back in time to when galaxy clusters were still assembling. In this work, we use observations and simulations to address ICL formation and assembly. We report on the detection of intracluster light within two proto-clusters at redshift 2 using deep HST images, suggesting that intracluster stars are already present within the core of proto-clusters. Using simulations, we analyze the origins of ICL in 100 massive, simulated proto-clusters from the Manhattan Suite simulations. Our goal is to pinpoint when and where ICL stars were born, the environments that shaped them, and the role of pre-processing in their assembly. We discover a surprising amount of ICL in the infall regions of proto-clusters, with a modest fraction in groups at redshift 2 to 4. Most ICL stars originated within galaxies and were later ejected during galaxy interactions. Our findings also reveal that galaxies hosting ICL stars in the past are more massive than the average galaxy population, a trend especially pronounced in groups. This suggests that massive galaxies, through processes like mergers, play a key role in ejecting stars into the intracluster medium. Together, these results shed light on the intricate and dynamic processes that give rise to intracluster light in the earliest stages of proto-cluster evolution.

334 How well do simulations resolve stellar stripping processes in galaxy clusters?

Cosmological hydrodynamical simulations are widely used to make predictions for the intracluster light (ICL), but the impact of numerical resolution on the tidal stripping of stars remains unclear. In particular, a simulation's ability to accurately capture the stellar disruption of satellite galaxies depends on both mass resolution and force softening, which influence the structure of galaxies and their dark matter halos and the efficiency of stellar stripping.

I examine how these factors affect stellar stripping efficiency across various orbits, satellite masses, and morphologies. While stripping is relatively insensitive to stellar mass resolution, resolving the central regions of satellite dark matter halos is crucial. Low-resolution simulations artificially flatten central density profiles, enhancing tidal stripping and leading to excessive stellar mass loss.

I find that dark matter mass resolutions of around 10^6 solar masses are required to reliably recover bulk ICL masses, suggesting that contemporary cosmological simulations may overestimate the total mass liberated. Finally, I discuss the implications of this over-stripping for the resolved and chemo-dynamical properties of the ICL.

Speaker: Garreth Martin (University of Nottingham)

335 The Main Progenitor Galaxies of Intracluster Light Stars

Although there is a developing understanding of the mechanisms by which the diffuse stellar component of galaxy clusters termed the intracluster light (ICL) is formed, no strong consensus has yet been reached on which objects the stars of the ICL are primarily sourced from. We have investigated ICL assembly in the Horizon-AGN simulation (a cosmological hydrodynamical simulation), and in this talk I will relay our findings for the bulk ICL contribution from galaxies with differing stellar masses preceding cluster infall, what range of galaxy masses are responsible for the vast majority of the ICL contributed by galaxies, and what objects are the most significant contributors of ICL stars in a typical cluster - all of which provides insightful context for utilising ICL to discern the dynamics and assembly history of a galaxy cluster.

Speaker: Harley Brown (University of Nottingham)

336 Modelling globular clusters in TNG50: predictions from dwarfs to giant galaxies

We present a post-processing catalog of globular clusters (GCs) for the 39 most massive galaxy groups and clusters (M$_{200} = [5\times 10^{12} - 2\times 10^{14}] \ \rm M_{\odot}$) in the TNG50 simulation. We tag GCs particles to all galaxies with stellar masses $M_{\odot} \geq 5\times 10^{6} \ \rm M_{\odot}$, and we calibrate the total mass of the GC system to reproduce the observed GC mass-halo mass relation for galaxies with M$_{200} \geq 10^{11} \ \rm M_{\odot}$ (corresponding to M$_* \sim 10^{9} \ \rm M_{\odot}$). Here, we explore whether an extension of the GC-mass halo mass relation to lower-mass dwarfs is consistent with current observations. We find good agreement between our predicted number and specific frequency of GCs in dwarfs with $\rm M_{*} = [5\times 10^6 - 10^9] \ \rm M_{\odot}$ and observations. Moreover, we predict a steep decline in the GC occupation fraction for dwarfs with M$_* \leq 10^{9} \ \rm M_{\odot}$, which agrees well with observational constraints.This declining occupation fraction is due to a combination of tidal stripping in all dwarfs plus a stochastic sampling of the GC mass function for dwarfs with M$_* < 10^{7.5} \ \rm M_{\odot}$. Our simulations also reproduce available constraints on the abundance of intra-cluster GCs in Virgo and Centaurus A. These successes provide support to the hypothesis that the $M_{\rm GC}$-$M_{200}$ relation holds, albeit with more scatter, all the way down to the regime of classical dwarf spheroidals in these environments.

337 Intracluster Light as a Probe for Dark Matter: Exploring SIDM and CDM with C-EAGLE Sim

The self-interacting dark matter (SIDM) model has garnered increasing attention as a potential solution to discrepancies between dark matter-only simulations and observations in small scales. SIDM predicts distinct tidal interaction histories compared to the cold dark matter (CDM) model, leading to differences in the evolution and distribution of intracluster light (ICL). In this study, we analyze galaxy clusters from the Cluster-EAGLE (C-EAGLE) zoom-in cosmological simulation, including two clusters re-simulated under identical initial conditions within a SIDM universe. Our findings indicate that dark matter is traced with the highest accuracy in the following order: brightest cluster galaxy (BCG) + ICL > gas > all stars > galaxies. Over time, the tracing performance improves for BCG+ICL and gas, whereas it declines for all stars and galaxies. BCG+ICL consistently serves as a reliable tracer, even at high redshift, while gas initially performs poorly but gradually improves, eventually becoming comparable to BCG+ICL. In the SIDM case, the gas distribution more closely resembles dark matter than in the CDM case. This suggests that in CDM, dark matter remains collisionless and behaves similarly to BCG+ICL, whereas, in SIDM, it exhibits mild viscosity and behaves more like gas. This study serves as an exploratory analysis to assess the potential of using ICL as a probe for constraining dark matter models.

Explosive Transients in the Present and Future Sky

Organisers: Aysha Aamer, Edward Charleton, Benjamin Godson, Joshua Pollin, Ana Sainz de Murieta, Xinyue Sheng, Ben Warwick

This session aims to explore the present and future sky of extragalactic transients. These explosive events provide invaluable insights into the universe’s most extreme environments, encompassing phenomena such as the diverse range of supernovae, tidal disruption events (TDEs), and superluminous supernovae (SLSNe). Beyond driving nucleosynthesis and shaping star formation, some of these events also serve as vital cosmological distance indicators.

Despite significant progress, many intriguing questions remain unanswered, and the arrival of extensive surveys like LSST and 4MOST promises to increase this discovery rate by a further order of magnitude. Simultaneously, a new generation of space missions (SVOM, EP) are already providing novel insights and challenges to our understanding of the high-energy regime. In this era of big data, machine learning and AI are being increasingly employed across various stages of survey pipelines, enabling more efficient and effective searches for these transients, but it is crucial to understand where these methods excel, and where they are limited.

The primary aim of our session will be to bring together members of the UK transient community to showcase new observational and theoretical results and current projects in the field. This includes talks on a broad range of extragalactic astrophysical transients to disseminate ideas and foster collaboration between those working across the complete spectrum of transient types, wavelengths, and messengers. We also encourage talks looking at the science being facilitated by current and future photometric and spectroscopic facilities to promote discussion on future projects.

338 Optimising Follow-Up of Gravitationally Lensed Supernovae Discovered with Rubin-LSST

Gravitationally lensed supernovae (glSNe) are powerful local probes of the Hubble parameter ($H_{0}$), as they are independent of the distance ladder and insensitive to the assumed cosmological model. Despite their rarity, the Rubin Observatory’s Legacy Survey of Space and Time (Rubin-LSST) will increase the sample of known glSNe by an order of magnitude. In this talk, we present a comprehensive analysis of follow-up strategies for glSNe discovered by Rubin-LSST based on how well time delays are estimated from an upgraded GausSN2 model. Within a hierarchical Bayesian framework, GausSN2 simultaneously models data in which the multiple images of the glSN are resolved and in which they are unresolved to achieve robust time-delay estimates. The model also accounts for chromatic microlensing, host galaxy dust extinction, and differential dust extinction in the lens galaxy in the statistical error budget. We apply this model to simulated glSN Ia systems with realistic Rubin-LSST data and varying amounts of space- and ground-based follow-up. Whereas without follow-up, the time delay can only be constrained to of order a week, with 4 epochs of resolved space-based data, the time delay constraint improves to of order 1.5 days. Furthermore, with sufficient optical to NIR wavelength coverage, we can constrain differential dust in the lens, and therefore lensing magnification, which is important to break lens modelling degeneracies. This work provides an important framework for best taking advantage of glSNe discovered by Rubin-LSST whilst maximising the impact of valuable and limited space-based follow-up for a precise $H_{0}$ estimate from time-delay cosmography.

Speaker: Erin Hayes (Institute of Astronomy, University of Cambridge)

339 Lensed Type IIn Supernovae with LSST: How Ultraviolet Suppression Shapes Detection Rates

Over the next decade, large survey telescopes, such as the Large Synoptic Space Telescope (LSST), are expected to yield hundreds to thousands of detections of gravitationally lensed supernovae, offering unprecedented advances in the study of these phenomena. Of particular note is the expected prevalence of Type IIn supernovae, which, with over 200 detections expected per year, dominate the predicted detection rates amongst lensed transients in previous studies. This is despite making up only 5-10% of observed non-lensed core-collapse supernovae.

In this talk, I will challenge this exciting result by modelling the effects of ultraviolet suppression - a deficit in the UV flux relative to the blackbody continuum - in the spectra of Type IIn supernovae to investigate how this affects the detection rates. I will describe the exciting physics of Type IIn supernovae and illustrate how they unlock some key insights into stellar environments and the terminal stages of the lives of giant stars. I will explain why they seem to be the ideal candidate for gravitationally lensed supernova detections with LSST, and therefore why they dominate over other supernova types in detection rate studies. Then, I will challenge this assertion by outlining the cause and effects of ultraviolet suppression, and whether it has a significant impact on the LSST detection rates of Type IIn supernovae, and their prospects as astrophysical and/or cosmological probes.

Speaker: Andrés Ponte Pérez (University of Birmingham)

340 The early-time light curves of type II and type IIb supernovae from the ATLAS survey

During the last decade, the increase in survey depth, cadence, and sky coverage has led to a significant increase in the number of discovered supernovae (SNe), and more importantly the number of SNe discovered soon after explosion. Discovering SNe within days of explosion enables investigation into the outer density profile of progenitor stars, and/or the presence of significant circumstellar material. Understanding the presence and diversity of this progenitor material can lead to strong constraints on the latter stages of stellar evolution. I will discuss the early time light-curves of both Hydrogen-rich SNe type II (SNe~II) and Hydrogen-poor SNe~IIb observed by the ATLAS survey. For SNe~II, we compare light-curve properties with the presence or absence of early-time 'flash' ionisation features, finding evidence that those SNe~II with/without such spectra features show distinct light curve properties. These results suggest a link between early-time interaction and later-phase transient properties of SNe~II.
In the case of SNe~IIb, we characterise the presence and frequency of early-excess in SNe~IIb light curves. We find a frequency of early-excess light curves of a sample of 63 SNe~IIb of between ~30 and 40%. In addition, we find that those SNe~IIb displaying an early-excess light curve appear to have longer-duration light curves, implying a link between the presence of an extended envelope and the bulk properties of the progenitor (i.e. the ejecta mass). I end this contribution with discussion of theimplications of these observational results on the progenitors, stellar evolution pathways, and mass-loss histories of SNe~II and SNe~IIb.

341 Shock Interaction Powering Late-Time Supernova Evolution: Tracing the Mass-Loss History of Massive Stars

Late-time shock interaction between supernova (SN) ejecta and circumstellar material (CSM) offers a powerful probe of the mass-loss history of massive stars and the dynamics of stellar explosions. This interaction is critical for understanding the final stages of stellar evolution and the diversity of core-collapse supernovae (CCSNe). While shock interaction signatures have been observed in a range of CCSNe, they vary significantly depending on the progenitor’s mass-loss history, the structure of the CSM, and the explosion dynamics. 

With a given opportunity, in the talk, I will explore late-time shock interaction as a key mechanism influencing the evolution of Type II SNe, focusing on the broader implications for the entire class. As a striking example, I will discuss SN 2023ixf, a nearby Type II SN in M101, whose late-time spectra exhibit prominent signatures of ejecta-CSM interaction (Kumar et al. 2025, MNRAS, 538, 659K). Observations taken nearly a year post-explosion reveal unique Halpha features and asymmetries that shed light on episodic mass loss occurring nearly 300-1000 years before core collapse. This detailed case study provides insight into the mechanisms driving shock interaction and highlights the role of progenitor mass loss in shaping supernova evolution.

By comparing SN 2023ixf with other interacting supernovae, I will demonstrate how late-time spectroscopy can uncover the diversity in pre-supernova mass loss and explosion dynamics. This study underscores the importance of systematic late-time observations in advancing our understanding of massive star death and the environments they shape.

342 Unveiling the complex mass loss of the transitional IIn SN 2024cld

Interacting transients provide invaluable insights into the final moments of the lives of massive stars, unveiling the mechanisms of pre-explosion mass loss, and tracing the amount, composition, and geometry of the CSM resulting from these processes.

I will present the transitional IIn SN 2024cld, discovered and classified just 12h post-explosion through the GOTO-FAST survey, and intensively followed for 200d after explosion. SN 2024cld shows marked similarities to SN 1998S and PTF11iqb: with strong flash-ionisation signatures close to explosion transitioning to persistent, narrow H emission all the way to +200d. High-resolution spectroscopy shows a sharp change in the structure of Halpha around +30d, providing evidence for two distinct CSM components, one we attribute to strong eruptive mass loss or binary shedding, and one tied to wind-driven mass loss.

Comprehensive imaging polarimetry also suggests changes in the asphericity of the photosphere as the ejecta sweeps the inner disk-like CSM, pointing towards further complexity in the mass loss prior to this. SN2024cld further underscores the chaotic and messy ends of red supergiant stars, driven by multiple mass loss mechanisms.

Speaker: Tom Killestein (University of Warwick)

Forging the elements: Understanding chemical evolution and stellar populations across cosmic time

Organisers: Conor Byrne, Stephanie Monty, Ankur Upadhyaya, Louise Welsh; co organisers: Nathan Adams, Karla Arellano-Cordova, Andreea Font, Robert Izzard, Chiaki Kobayashi, Christopher Lovell, Katherine Ormerod, Vadim Rusakov, Aayush Saxena, Ragandeep Singh Sidhu, Charlotte Simmonds, Elizabeth Stanway

The origin and build-up of chemical elements in stars, dust and gas throughout the Universe is a fundamental question in modern astrophysics. Addressing this requires understanding stellar nucleosynthesis, stellar evolution and galaxy evolution across all epochs and length scales. Progress hinges on combining constraints from cutting-edge observational facilities with state-of-the-art theoretical models of stars, the Milky Way, galaxies, and the interstellar and intergalactic medium.

The advent of JWST has revolutionized studies of chemical and galactic evolution at the earliest epochs. Interpreting these observations requires advanced stellar, galactic and chemical evolution models encompassing many physical processes, including: nuclear and atomic physics, chemistry and dust formation. Combining and discussing the results from these different areas is necessary to forge a unified model of the early Universe.

One area in which models need refinement is accurately representing the conditions in the distant Universe. Observations of extreme stellar populations such as young, massive stars at low metallicity and future studies with ELT are valuable tools to bridge the gap between high- and low-redshift stellar populations. A close relationship between observations and models is essential; high-quality observations constrain models, while improved models provide better insight into early chemical and galactic evolution.

This session targets these open questions from observational and theoretical perspectives, involving stellar and galactic astronomers. Through short talks and focused discussion, we will bring together the considerable leadership and expertise of UK-based researchers in these fields, gain insight into uncertainties and limitations of data interpretation, and outline a roadmap to addressing these challenges.

343 Galactic Chemical Evolution with Hybrid Stars – From Structural Assumptions to Yields

Thorne-Żytkow Objects (TŻOs) are a class of hybrid stars, originally proposed by Thorne & Żytkow (1977), consisting of a neutron star core, surrounded by a diffuse, convective, giant envelope. Recent work by Farmer et al. (2023) to produce models of TŻOs in MESA has reignited interest in structures of these objects.

All plausible formation mechanisms for TŻOs involve a binary interaction, and the mechanism preferred from both the standpoint of population synthesis studies, as well as hydrodynamical simulations involved a CEE event. The effective TŻO formation rate remains an open question, but if even a modest proportion of these binary systems form TŻO, then the population of TŻOs in the Galaxy could be expected to have a significant effect on Galactic Chemical Evolution.

We place central boundary conditions directly at the surface of the neutron star and make use of an Eddington accretion prescription, set by the opacity at the base of the convective envelope to self-consistently model the release of gravitational potential energy, as well as to model to entire radiative region, or "halo" of the Thorne-Żytkow Object.

We discuss our solutions and the implications of the possible existence a parallel series of equilibrium structures for TŻOs. We also discuss the important implications of our structure solutions for possible nucleosynthetic pathways in our models, and the further effects of this on yields of these post-XRB systems, and on Galactic Chemical Evolution as a whole.

Speaker: Alexander Hackett (CEICO - FZÚ-AVČR - The Physical Institute of the Czech Academy of Sciences)

344 Black Holes to Pair Instability Supernovae from Stellar Evolution

The Pair Instability (PI) boundary was previously thought to be robustly determined by theory as starting at $~50 M_\odot$. Recent Gravitational Wave observations such as GW190521 suggested otherwise, igniting a flurry of theories and predictions, which has had significant follow-on implications for stellar populations in Population II and III environments. Stars above the PI boundary are expected to undergo one or more pulsations before collapse to a black hole, or be fully disrupted by a PISN, enriching the local environment. Stars below the boundary are expected to collapse to black holes without a supernova, thus not enriching the local environment in their final fates and only through wind mass loss, which is expected to be very small at low metallicity. Thus the exact location and progenitor stars of BHs/PI forms an important question in chemical evolution in low metallicity galaxies. By changing stellar evolution parameters such as mass, metallicity, rotation, overshooting, and semiconvection, we have explored the previously theorised PI mass gap with stellar evolution models. We also include mechanical mass loss, which provides an enhancement to the mass loss rates, especially for low metallicity stars. From this we find that the maximum black hole mass could be as high as $90 M_\odot$ under specific conditions, but that with more physically moderate assumptions, the Pop II and Pop III stars could fill the PI gap with black holes in low metallicity environments.

Speaker: Ethan Winch (Armagh Observatory and Planetarium)

345 Environmental Dependence of the Mass–Metallicity Relation in Cosmological Hydrodynamical Simulations

Understanding how environments impact galaxy evolution is pivotal in unraveling the interplay between internal processes and external environmental effects. Using cosmological hydrodynamical simulations (EAGLE, IllustrisTNG), we explore the environmental dependence of the gas-phase mass-metallicity relation (MZR) from z∼2.3 to z=0. We found that, at fixed stellar mass, central galaxies in massive halos exhibit lower metallicities than those in low-mass halos, driven by pristine gas accretion at high-z and AGN-driven outflows at low-z. Conversely, satellite galaxies in massive halos are more metal-rich due to suppressed gas replenishment and stripping. High-z protoclusters reveal a dichotomy: massive galaxies are metal-poor (dominated by gas-rich centrals), while low-mass galaxies are metal-rich (influenced by satellite processes), aligning with observations like MAMMOTH-Grism. These results highlight distinct environmental mechanisms for centrals and satellites—accretion dynamics and AGN feedback versus strangulation and stripping—underscoring the critical role of environment in modulating metallicity across cosmic time. Our findings bridge simulations and observations, offering a framework to decode environmental signatures in galaxy evolution.

Speaker: Kai Wang (Durham University)

346 The evolution of dust and metals in galaxies back to z~9 from a simulation perspective

In this talk, I will present a new view on the chemical elements in stars, dust, and gas at high redshift from the cosmological-scale galaxy evolution simulation, L-Galaxies.

L-Galaxies is currently the only cosmological simulation to simultaneously include models for detailed chemical enrichment, binary stellar evolution, and dust formation. This allows L-Galaxies to track the precise build-up of 118 chemical elements and a range of dust species back to very high redshift, enabling direct comparisons to the latest observations from JWST and providing predictions for up-coming surveys using e.g. ELT.

I will present L-Galaxies results stretching back to z~9, including (a) dust-to-gas and dust-to-metals ratios in galaxies compared to ALMA data, and (b) oxygen abundances and N/O ratios in star-forming galaxies compared to JWST data, and (c) the evolution of the total dust and metals budget in the Universe in various phases compared to recent DLA observations. Considering a combination of dust and metals in this way provides unrivalled constraining power for simulations, allowing us to pin-down the relative importance and interplay of the various processes driving chemical evolution at early times.

I will finish by outlining some up-coming plans for L-Galaxies, including direct comparisons to strong-line and electron-temperature metallicity measurements using synthetic spectra, and the development of a user-friendly version of the simulation specifically designed for use by observers.

347 Exploring the impact of different star formation scenarios on high-redshift spectroscopic observables with MEGATRON

Various solutions have been proposed to solve the high-redshift `bright galaxy problem', such as more efficient star formation, bursty star formation, and variable initial mass functions. While equally interesting, each scenario must also differ in how these stellar populations couple to the interstellar medium (ISM) through stellar feedback. In this talk, I will present first results from the MEGATRON suite of high-resolution cosmological radiation hydrodynamical zoom simulations which for the first time feature non-equilibrium chemistry and heating/cooling processes coupled to on-the-fly radiative transfer.
Each simulation explores one of these high-redshift star formation scenarios, coupled to detailed prescriptions for the formation, evolution, and feedback from population II and III stars, including: stellar winds, supernovae, and hypernovae.

Using these simulations, I will discuss the impact that these different star-formation scenarios have on the chemical evolution and phase structure of the ISM. Furthermore, using the unique capabilities of the simulations, I will trace these differences through to their impacts on direct observables: such as line ratios and diagnostic diagrams, C/O and N/O abundances, mass-metallicity relations, ionizing efficiencies, and UV continuum slopes. At each step, results will be contextualized alongside the latest JWST observations. All of this will begin to build directly falsifiable predictions through quantities which are already being directly measured at high-redshift with JWST, allowing us to better understand star-formation processes in the early universe.

348 On the Observability of Population III stars in the MEGATRON Simulation

The advent of JWST has allowed us to peer further into the Universe than we've ever been able to before. With over 20 galaxies observed beyond redshift 10, we are now able to observe the formation of galaxies at a time where we still expect the formation of population III (Pop. III) stars. In this talk I will introduce the MEGATRON simulation of a Milky Way-mass galaxy at redshift 0, and its prescription for the formation of individual Pop. III stars at Cosmic Dawn. MEGATRON features a comprehensive out-of-equilibrium chemistry network of 82 species coupled to multi-frequency on-the-fly radiation transfer from stellar SEDs. This enables us to model a multi-phase ISM through accurate cooling curves, to track and resolve the chemical enrichment and ionization from stellar feedback, and generate galaxy spectra to compare with observations. We calculate spectra for all galaxies forming Pop. III stars and show that even for galaxies with large bursts of Pop. III formation, their observational signatures are much too dim to be observed with JWST. We also track Pop. III stars through particle tagging to redshift 0 and show that a significant number of Pop. III stellar remnants reside in sub halos.

349 An exact method for pairing stars to form binary systems

The statistical properties of a population of binary stars are determined in large part by the joint distribution of the masses of their components at their time of formation. These masses determine the binary stars' subsequent evolution. However, this joint distribution is known neither from first principles, since theory is insufficiently developed, nor from observation, since observational surveys instead report the distribution of the masses of the ionized components of the binary stars (the initial mass function) and the conditional distribution of the masses of the secondary stars given the mass of the primary star (the pairing function). Here we show that the joint initial mass function (joint IMF), the initial mass function (IMF), and the pairing function (PF) are related by a simple integral equation. This equation constrains the forms that the IMF and PF may take even in principle. Given valid IMF and PF it typically admits a unique solution for the joint IMF. Using this solution we may find the distribution of the masses of the primary stars (the primary initial mass function). In the high-mass limit this primary initial mass function (primary IMF) is twice the value of the IMF and in the low-mass limit vanishes, regardless of the PF. Knowledge of the primary IMF allows us to initialize population synthesis models exactly and, in particular, to exactly specify the number of supernova progenitors at initialization. We explore the consequences of this for the late-time supernova abundances and iron yields computed using these models.

17:35 Closing Remarks

18:00 OCW artwork unveiling

19:30 Social Event: Board games

Thursday 10 July

08:00 Registration and set up

Community EDI initiatives in Astronomy and Geophysics

Organisers: Katrine Glasscock, Marieta Valdivia Lefort, Laura Wolz; co organisers: Dominic Bowman, Andrew Curtis, Karen Devoil, Benjamin Fernando, Farideh Honary, Kirushney Kalamohan, Robert Massey, Nathan Mayne, Ingrid Murray, Jasmine Sandhu, Jane Smith, Matthew Temple, Luis Welbanks

A persistent challenge in Equity, Diversity, and Inclusion (EDI) is creating spaces to exchange ideas, share successful initiatives, and start critical conversations that foster meaningful change. The fields of astronomy and geophysics face widespread issues, such as imposter syndrome, balancing family life and the transient nature of research posts, and bullying and harassment. These issues significantly impact the ability to attract and retain diverse scientists and create inclusive workplaces. Addressing these challenges requires evidence-based, localised EDI practices that consider intersectional perspectives and support underrepresented groups, including LGBTQ+, ethnic minorities, disabled, neurodiverse, and first-generation scientists.

This session invites contributions from individuals who have designed and hosted impactful EDI projects or community events, such as EDI forums, EquiTea, and online platforms, aimed at improving equity and accessibility within their institutions. We encourage participants to share best practices for planning, delivery, and evaluation of EDI initiatives, as well as resources to support sustainable change. By showcasing the experiences and successes of our community, we aim to spark meaningful conversations and empower the astronomy and geophysics communities to build more equitable and supportive spaces.

09:00 Prep time

350 RAS Demographics and Research Interests Survey

We present the results of the 2023 survey of the demographics and research interests of the UK astronomy and geophysics research community, offering a unique insight into the composition of this workforce. This is the most recent in a series of surveys commissioned by the Royal Astronomical Society dating back to 1988 and is the most recent of the three surveys which have sought detailed demographic data, collected in this case after Brexit and the height of the Covid pandemic.

The survey encompasses the various protected characteristics of researchers, the ways in which employees and postgraduate students use their time, both in research and in other areas such as outreach and administration, the research interests and major instruments used by respondents, and gives us information on the career intentions of early career researchers.

Results indicate persistent challenges for our efforts to develop a workforce that reflects the balance of wider society, something that remains of great importance to the UK, even as it is undermined across the Atlantic, and how that workforce can be productive. We will consider how these findings should shape the priorities of the RAS, and what practical steps our organisation, and the wider scientific community, should take in the years ahead.

351 The Path to Expertise: Trajectories of Talented Women in Astronomy

Astronomy is fundamental to human development, driving technology and innovation while generating knowledge that helps humanity understand the universe (Sturrock et al., 2019). However, women remain significantly underrepresented in this field. While many women leave astronomy, little is known about those who persist and succeed. The purpose of this study was to explore the events, skills, experiences, milestones, and individuals that have contributed to the development of women's talent throughout their trajectories in astronomy. Using a qualitative study with a feminist approach, in-depth interviews with a visual component were conducted with five talented women in astronomy. The findings reveal the micro, meso, and macro levels of influence that have shaped their paths, as well as the intensity and direction of these influences throughout their journeys. The implications for studying talent development in women astronomers are discussed.

352 Report on the EAS 2025 Session “An Intersectional Approach to EDI Strategies”

Around the globe, homophobia, queerphobia and racism are on the rise. Against this social background, it is imperative that astronomy is a safe space. Yet despite the great work being done across many institutes, astronomers belonging to marginalised groups (such as women, LGBTQ+ individuals, Black people, and people with disabilities) continue to face significant challenges and obstacles to research. For example, LGBTQ+ astronomers are more likely to be professionally devalued, and harassed by their peers at work, and nearly half of women of colour in astronomy regularly feel unsafe in the workplace and at conferences.

There are many initiatives in place to try and reduce discrimination, however most focus exclusively on the gender imbalance. Whilst this is an important aspect of diversity, overlooking other groups risks further marginalisation. An intersectional approach to EDI strategies is necessary to ensure that no astronomer is left behind. Such EDI initiatives are crucial for ensuring a safe, welcoming workplace. In doing so, we include scientists from all backgrounds, which increases our creativity and mobility. Collectively, this is the responsibility of all of us.

We will convene the session “An Intersectional Approach to EDI Strategies” at EAS 2025, and will use this session at NAM 2025 to report on our findings, highlighting the brilliant work being done both in the UK and Europe, and internationally.

Speaker: Dr Izzy Garland (Masaryk University)

353 P-Star: Powering Astronomy in Pakistan

In 2022 the last cohort of students in Space Sciences graduated from the University of the Punjab in Lahore, Pakistan. Key issues causing the discontinuation are (1) a perceived lack of paths to employment from such courses and (2) lack of access to state-of-the-art research resources. P-Star is addressing both concerns simultaneously and helping support local experts to kick-start a renaissance of Space Science research in the country.

While numerous astrophysical computation codes and observational data repositories are “open source”, their usage is often severely limited on the wider global stage by (1) knowledge of (1) their existence and availability and (2) the relevant access methods and basic usage examples for each individual repository. P-Star is assembling a team of astronomy experts spanning the UK, EU, USA, and Asia. We identify and develop free undergraduate and masters level teaching materials that can make graduates more employable in places like Europe, America, India and East Asia. Students travelling to these countries will grow their experience, and increase the potential to seed new research themes and opportunities in their home countries. Our materials are supplied to our target institutions, and after proof of concept is established and export controls applied, an open-source repository will be made available.

Current results of P-Star include university-level and grassroots events in Lahore, and ongoing co-supervision of masters projects. Our partners have recently secured infrastructure funding for astronomical observatories in Pakistan and we seek to continue building our team to better support such endeavours.

10:05 Q&As

Radio Astronomy in the build up to the SKAO

Organisers: Johannes Allotey, Emmy Escott, Catherine Hale, James McGarry, Lucy Oswald, David Williams-Baldwin

The field of radio astronomy will soon be revolutionised by the arrival of the Square Kilometre Array telescopes. Now that the first fringes have been recorded with SKA-Low, and the first SKA-Mid dish is in place, it is time to look to the future of radio astronomy and the scientific opportunities coming up, and to reflect on the state-of-the-art science with precursor/pathfinder telescopes.

The goal of this session is to showcase the breadth of work conducted with SKA precursor and pathfinder instruments, such as e-MERLIN, MeerKAT and LOFAR across a diverse range of science goals, and to provide an opportunity for discussion and connection over plans for future science with the SKA Observatory (SKAO). We also will likely include discussion from invited speakers to update on the SKAO and the Science Regional Centres.

The session will be organised and led by members of the SKAO UK Early Career Researcher (ECR) committee, and will build on the success of the equivalent session at NAM2023.

354 Anomaly detection techniques for transient detection in the era of the SKA

SKA pathfinders can sample wide swathes of the radio sky with unprecedented sensitivity and cadence. As a result, we are now discovering novel radio transients across an immense range of astrophysical regimes - from flare stars to FRBs. I will discuss recent, serendipitous discoveries being made with the MeerKAT and ASKAP radio telescopes. I will show how unsupervised machine learning techniques accelerate the search for interesting and anomalous sources in large datasets such as those expected from the SKA. These anomaly detection models can, with the use of active learning strategies, be customised to find not only anomalies, but those that are verified as interesting systems for a particular science case. The tested models show great success in recovering transients in our large dataset, reducing the volume of sources for vetting by an order of magnitude. Following these successes, I will show how the application of these anomaly detection techniques to ASKAP data has uncovered a huge range of transients including long period transients, further stellar flares and new radio detections of X-ray binary outbursts. I will demonstrate how the huge data rates and superb sensitivity of the SKA necessitates fast techniques for searching for anomalies and show that these techniques provide a way to detect transients at scale and on-the-fly, revolutionising our understanding of the dynamic radio sky.

355 VLA broad-band monitoring of the flux-ratio anomalous lens system B2045+265 as a probe for dark matter

CLASS B2045+265 is a gravitationally lensed system where a radio-loud background galaxy is lensed by a radio-loud foreground galaxy, producing four lensed images. The flux-ratios of the four lensed images are known from previous observations to be inconsistent with the predictions from a simple singular isothermal ellipsoidal (SIE) model for the foreground mass distribution. This may suggest the presence of unresolved substructure or variability within the system.

As part of the Lensing over Frequency and Time (LoFT) project, we conducted broadband interferometric observations of CLASS B2045+265 using the VLA at 12–18 GHz over a 63-day monitoring period. With this high-resolution data set we have conducted a detailed investigation of the variability over time and frequency of the system, allowing us to explore the potential role of the dark matter substructure in producing the observed flux-ratio anomalies.

Our analysis demonstrates that such wide-band observations can probe the physical properties of lensing systems with a level of detail comparable to what SKA-MID will achieve in Band 5. By showcasing the capabilities of current instruments, this work highlights the potential of SKA-MID to extend these studies with higher sensitivity, faster processing, and superior RFI mitigation. Future SKA-MID observations will enable more robust tests of flux-ratio anomalies, ruling out variability-related effects, and offering unprecedented insights into the small-scale structure of dark matter in lensing systems.

356 Finding Complex Radio Sources in the Rapid ASKAP Continuum Survey using Self-Organising Maps

The SKA will identify tens of millions of new sources - but identifying and classifying their morphologies will require novel, robust, reliable, and efficient methods. In particular, complex sources are of significant interest thanks to (e.g.) wide-angled tails being "weather vanes" for galaxy cluster activity, and the possibility of new discovery space for galaxy evolutionary pathways.

One way of addressing the wealth of data is to use machine learning, and in particular, Self-Organising Maps (SOMs). In this presentation, we detail how we have mapped 251,259 multi-Gaussian complex sources from Rapid ASKAP Continuum Survey (RACS) onto a SOM with discrete neurons. We use Euclidean distance to identify the best-matching neuron for each source and assess the reliability through visual inspection of a subset of sources. We show that sources for which the Euclidean distance to their best matching neuron is ≲ 5 (accounting for approximately 79% of sources) have an estimated > 90% reliability for their SOM-derived morphological labels. Our catalogue of complex radio sources from RACS with their SOM-derived morphological labels from this work will be made publicly available for inspection.

357 On-The-Fly Mapping of the MeerKLASS Survey

The MeerKAT telescope is a precursor for the SKAO, the next generation radio observatory. We have been successful in being awarded observing time on MeerKAT for a pathfinder SKAO-project to conduct a wide-field (approx. half of the whole southern sky) survey, called MeerKLASS. Several hundred hours of data at 580-1015 MHz have already been collected and we exploit a technique called On-The-Fly Mapping (OTF) which allows us to image the sky extremely quickly (300 square degrees per hour), at full angular resolution (approximately 15 arcseconds) and with high sensitivity (~30 muJy). This survey will have huge legacy value and also allow cosmological studies such as measuring the dipole induced by the Milky Way’s motion through its effect on the radio source count.

In this talk we will present the OTF data reduction pipeline and show results from our initial data release. We will demonstrate the image fidelity and accuracy of our continuum sky maps and discuss the potential for studies of polarised, variable and extended low-surface brightness sources.

358 Radio-AGN across the galaxy population: implications for fuelling and feedback

Active galactic nuclei (AGN) can have a significant effect on their host galaxies by regulating their growth or suppressing star formation (known as AGN feedback). Of particular importance for massive galaxies and clusters are jet-mode AGN which display powerful radio jets and keep galaxies ‘red and dead’ once quenched. However, until recently, the cosmic evolution of jet-mode AGN has remained largely unconstrained beyond z~1. The LOFAR telescope has been undertaking one of the deepest wide-field radio continuum surveys to date: this represents a novel sample to statistically study the evolution of AGN activity and feedback across cosmic time. Using this sample, I will present the first robust measurement of jet-mode AGN feedback out to z ~ 2.5. We discover a new dominant population of jet-mode AGN hosted by star-forming galaxies at high redshifts, that has not been previously observed. We find that the bulk of the AGN heating output is performed by this new population in the early Universe, highlighting their importance in early galaxy evolution. I will also present a detailed analysis of the host galaxy properties which finds evidence that this new class of AGN within star-forming galaxies is fuelled by a different mechanism compared to their quiescent counterparts. These results showcase the power of deep wide-area radio continuum surveys in the pre-SKA era in characterising the nature of the faint AGN population across cosmic time.

359 Role of environment in the jet powering mechanism of radio quasars - insights from the LOFAR Two-metre Sky Survey (LoTSS)

A key component of AGN feedback is the injection of kinetic energy from radio jets. However, there’s a fundamental lack of understanding of why quasars, otherwise very similar, have such a wide range of radio jet powers and, therefore, the impact of AGN jets. Using large samples from LoTSS DR2 coupled with a Bayesian parametric model, we can separate and quantify the jet and host galaxy contributions to quasar radio emission. We demonstrate that the traditional radio-loud/quiet quasar classification fails to reflect the physical origin of radio emissions. Instead, our model allows for redefining radio AGN populations based on physical processes, which enables us to robustly measure the evolution of quasar jet power with environmental factors on large and small scales. We discovered a positive correlation between quasar jet power and angular clustering, suggesting a coevolution between jet production and halo mass. Quasars dominated by jet activities are 10 times more clustered than those without strong jets. Quasars with more massive black holes are also more clustered, albeit with a weaker signal, implying that accretion mode differences are less critical in the production of strong jets. Finally, we will present results from the first joint LOFAR-Euclid study on the role of galaxy mergers in triggering quasar radio jets. This not only reveals the role of small-scale environment in jet production but also showcases the potential of future Euclid-SKA synergetic studies, thanks to their exquisite spatial resolution and surface brightness sensitivity.

10:12 Poster Flash Presentations

Astronomy futures – new missions, facilities and the support needed to exploit them

Organisers: Martin Barstow, Giulio Del Zanna

Important scientific advances in astrophysics often depend on combining specialised observations with state-of-the-art theoretical models. This requires new missions and instruments (space/ground-based) targeted on specific science goals. Such facilities need a supporting infrastructure and a critical mass of well-trained researchers, without which the science outcomes cannot be achieved.

We propose a forum for the presentation and discussion of new missions and facilities covering the wide astrophysics and planetary science interests of the UK community. Importantly, we will also address their requirements for multi-disciplinary support, covering a diverse range of topics including new technologies, laboratory astrophysics, computational needs and data analysis tools to ensure that the UK benefits fully from its investments. We will also look at training requirements for young researchers, e.g. developing new skills (e.g. AI, machine learning, code development) or recovering historically important, but neglected, underpinning knowledge (e.g. atomic and molecular physics – measurements and theory, physics modelling including radiative transfer). This key support and training is often neglected in facility planning.

Traditionally, NAM sessions are organised by science subject. However, facilities and infrastructure typically encompass many research areas and the problems often overlap. We will address shared problems spanning disciplines to the benefit of the astronomical and planetary science community at large. The meeting will be structured in a way that promotes discussion with a panel of selected experts, introduced by a number of contributed / keynote talks. The programme will include any new facilities that are being proposed or are approved and under development.

360 The Solar Atmospheric Modelling Suite: First Steps and Future Plans

Accurate modelling of the solar atmosphere is essential for understanding the energy flow and build-up that underpins the heating of the solar chromosphere and corona, and drives eruptions and flares. Such a model would need to be able to capture the fundamental physical, radiative and ionisation states of the vastly different atmospheric layers of the Sun and the complex coupling between them. However, no model exists with the capability to accurately capture all the key processes of the different parts of the atmosphere, but one is necessary to understand the cutting-edge observations produced by new facilities and provide the much-needed step-change in our understanding of how the solar atmosphere works. In this talk I will present our proposal to develop a software framework (the Solar Atmospheric Modelling Suite - SAMS). We have been funded to build a modular code containing an exascale-ready, GPU-accelerated MHD engine coupled with a wide range of physics modules including 3D radiative transfer, updated atomic models and multi-fluid capabilities. SAMS will also include an integrated pipeline to take the simulation output to provide synthetic observables. I will provide an overview of what will be our first steps and our future plans and how we aim to engage the whole community in the project.

361 Operating the Largest Submm Single Dish Facility in the World

The Atacama Large Aperture Submillimeter Telescope (AtLAST) aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned sub-mm telescopes. With its 50m dish and 2 degree field of view, the strength of AtLAST is in science where a large field of view, highly multiplexed instrumentation and sensitivity to faint large-scale structure is important, from the gas and dust that fills and surrounds galaxies to the chromosphere of our own Sun. To deliver this science, AtLAST will build on the experience acquired from operating other facilities whilst introducing innovative practices to ensure sustainable operations and a work environment that fosters diversity, equity and inclusion. Operations will be science driven, with a flexible scheduling system and variety of observing modes to accommodate the wide variety of science cases. AtLAST is expected to have a tremendous legacy value given the different imaging and spectroscopic surveys the observatory will conduct along with PI driven science. With the goal of making all this data available to the community, AtLAST will require dedicated infrastructure including a data archive with long-term curation and accessibility and interoperability with other sub-systems. Multiple operations centres will be set up around the world to bring operations closer to researchers and the public. A tailored user support model will be implemented including early (and continuous) training. All of this is being planned with the aim of 30+ years of operations.

Speaker: Mark Booth (UK ATC)

362 Tools for the Future: Solar Physics Missions beyond Solar Orbiter

The international solar physics community currently enjoys access to a broad range of world-leading ground and space-based facilities in which the UK plays major hardware and science leadership roles (e.g. STEREO, Hinode, DKIST and Solar Orbiter (EUI, SPICE, SWA and MAG). UK leadership through these existing missions and facilities has led to significant roles (science and instrumentation) for the UK in the next generation of solar missions currently in development: MUSE (Multi-slit Solar Explorer) and SOLAR-C. Together these two missions are perfectly suited to addressing the major outstanding questions that were identified by the ESA/JAXA/NASA Next Generation Solar Physics Mission science definition team. The combination of SOLAR-C’s broad temperature coverage and MUSE’s high cadence data will for the first time properly capture the multi-scale physical processes that dominate the solar atmosphere.

In this presentation I will give an overview of the capabilities of MUSE and SOLAR-C and the UK’s current role. I’ll then look further forward to how the UK might further leverage current roles for greater return, as well as to new mission and instrument concepts where the UK is currently either leading developments or providing critical science expertise.

Speaker: Sarah Matthews (UCL)

363 SIRIUS - Stellar & ISM Research via In-orbit Ultraviolet Spectroscopy

SIRIUS is a small space science mission designed to study the environment surrounding our Sun and nearby stars in the Galaxy, out to distance of 100-200 parsecs. The scientific programme will be executed by a high-resolution (resolving power of 5000) extreme ultraviolet spectrograph covering the wavelength range 170-260Å.

The mission has been funded by the UK Space Agency as part of their Science Bi-lateral Programme. The instrument team and the mission science are led by the University of Leicester with contributions from other UK groups. They payload will be provided by an international consortium with partners from Germany, Spain and Belgium. The wider project consortium includes industry partner BAE/In-Space Missions (spacecraft and operations) and Oxford Space Systems (telescope deployment).

SIRIUS is piloting a new approach to space science, delivering high quality, observatory class science at significantly lower cost than by “traditional” programmes. The instrument applies novel techniques to deliver high sensitivity in a small package and makes use of high TRL off-the-shelf mission solutions and a ride-share launch. The estimated cost of the mission is £50-53M. It is well-suited to the recent ESA call for mini-F and F3 missions.

This paper will describe the SIRIUS instrument and its scientific capabilities, with a particular focus on the need for stellar spectral modelling and consequent atomic data.

364 Designing DiRAC-4: Supercomputing for computational cosmology

We present updates on the design process for the STFC DiRAC-4 facility, including the Science Case, Technical Case, and the user engagement process.

365 ESO and its Office for Science in Chile

The European Southern Observatory (ESO) operates the La Silla and Paranal observatories, and we are constructing the Extremely Large Telescope (ELT) on Cerro Armazones. ESO has offices in Garching, Munich, Germany and also Vitacura, Santiago, Chile. The Office for Science (OfS) in Chile coordinates the research activities of around 100 astronomers on the ESO-JAO campus in Santiago. We offer research fellowships, studentships and a range of other possibilities for astronomers of all career stages to collaborate with ESO astronomers in Chile. In this contribution, I will give a brief overview of ESO's current and future facilities before focusing on collaboration opportunities offered by the OfS. I will outline the ESO-Chile fellowship - a prestigious opportunity for early-career scientists to develop their research while obtaining experience of operations of the preeminent ground-based observatory in the world. The Chile studentship offers the possibility for students to come to ESO from between six months to two years to work on collaborative research projects and engage in short observatory trips. ESO is building the most advanced ground-based telescope, and is already planning the next large project (see 'ESO Horizons'). With this contribution I hope to further develop collaboration between ESO Chile and the UK astronomy community.

366 High resolution X-ray spectroscopy: XRISM as a pathfinder for newAthena

High resolution X-ray spectra are key to understanding the dynamics of hot gas. I will review some of the new results from the JAXA/NASA/ESA calorimeter XRISM/Resolve, which give the first high sensitivity/high resolution spectra above 6 keV. I will focus on the winds associated with accretion flows in strong gravity, the ultrafast outflows seen from Active Galactic Nuclei (AGN) which may be a major component of AGN feedback, controlling the starformation powered growth of the host galaxy. I will show how we get further insight into the launch processes by comparison to the very different winds seen from the stellar mass accretion flows and show how a new, larger area instrument will solve some outstanding issues in understanding the origin of these outflows.

Speaker: chris done (university of durham)

367 The (Uncertain) Future of Atomic Data for Astrophysics

Accurate atomic data are a cornerstone of astrophysical research - vital for interpreting the spectral analyses that drive our understanding of the Universe. Despite their importance, much of the atomic database (especially for elements beyond the iron group) remains based on measurements from the 1960s or earlier, which now fall far short of current, high-accuracy demands. The weakest link in modern astronomical spectral analyses is often poor quality atomic data, and at least order-of-magnitude improvements in accuracy are urgently needed. With the next generation of telescopes and surveys on the horizon, these demands are only set to increase.

The astronomy community often assumes that there are vast numbers of researchers dedicated to measuring these vital atomic data – unfortunately there are not! The number of researchers conducting these crucial experiments has been steadily decreasing, without younger researchers to replace them. This diminishing expertise poses a grave threat to the future of the field - once lost, it will be impossible to meet the growing demands of modern astrophysics. The recent closure of the two leading institutes for experimental atomic spectroscopy in the United States only underscores this precarious future for the field.

This talk will give an overview of the current state of atomic data for astrophysics and explore ongoing efforts to secure the future of the field. With the right support, the UK is ideally positioned to extend its leading role in experimental atomic spectroscopy, ensuring that we remain at the forefront of astrophysical discovery for decades to come.

368 Atomic data for astrophysics and their benchmarking

I summarise the UK APAP work led by N.R.Badnell to provide atomic data for astrophysics and my efforts to preserve some of them for posterity.
The UK was at the forefront in this area internationally but has entered a dark age.

I will then outline the status and the programme of benchmarking them against high-resolution astrophysical and laboratory spectra, in preparation for future missions.

Some spectral regions such as the EUV are in a satisfactory situation, especially where we had sufficient high-resolution observations.
The UV is still missing a lot of atomic data and improved modelling.
The X-rays also require significant improvements to match future observations.
Finally, the soft X-rays around 10 nm and the near infrared around 2000 nm are nearly unexplored.

10:17 Discussion and Q&As

Illuminating the Faintest Galaxies: Dwarf Galaxies as Probes of Dark Matter, Feedback, and the First Stars

Organisers: Alejandra Aguirre-Santaella, Shaun Brown, Ting-Yun (Sunny) Cheng, Jessica Doppel, Isabel Santos-Santos, Joaquin Sureda

Dwarf galaxies are the most numerous yet faintest type of galaxy in the Universe. As the most dark matter dominated systems in our Universe they offer a powerful laboratory to probe the nature of this elusive form of matter and search for potential decay signals. Their observed abundance and distribution can place strong constraints on different dark matter models.

Dwarf galaxies also serve as powerful tools for exploring the limits of galaxy formation, as they form in the smallest haloes. Their shallow potentials provide an excellent testing ground for feedback processes, such as supernovae, stellar winds, and AGN feedback. At the faintest end of the luminosity function, ultra-faint dwarfs are believed to be relics from the epoch of reionization, providing insights into the physics of reionization, the first stars, and early galaxy formation.

In the local Universe, dwarf galaxies offer the most detailed studies of stellar populations, kinematic analyses, and chemical abundances. These observations are critical benchmarks for validating and refining predictions from cosmological simulations. Upcoming facilities and surveys such as Euclid, LSST, Roman, WEAVE, 4MOST, SDSS-V, SKA, CTA and MeerKAT, will soon provide deeper and higher resolution observations for countless more dwarf galaxies, revolutionising our view of the Universe in the low-mass regime.

This session aims to foster interdisciplinary discussion and collaboration between observers and theorists working on dwarf galaxies from the classical to the ultra-faint regime. As a world leader in dwarf galaxy science the UK is well placed to fully exploit this new wealth of data.

09:00 Welcome remarks

369 Distribution-function models for binary-rich ultrafaint galaxies

Ultrafaint dwarf (UFD) galaxies are dominated by dark matter, the distribution of which may be inferred from the kinematics of that galaxy's stellar population. Star-by-star observations are available for the satellite UFD galaxies of the Milky Way, making them uniquely good laboratories in which to test cosmological predictions at the smallest scales. However, the kinematics of these galaxies are complicated by the presence of binary stars, which alter the stellar velocity distribution. In particular these binary stars increase the galaxy's stellar velocity dispersion, which is related to the total galactic mass by the virial theorem. Without correctly eliminating or accounting for binary stars we may therefore overestimate the masses of UFD galaxies or even confuse star clusters for UFD galaxies. Here we write down the probability density function for the observed line-of-sight (LOS) velocity of a stellar population containing both visual and spectroscopic binary stars, which we then use to determine the effect of those binary stars on the observed LOS velocity dispersion. For the coldest UFD galaxies the fractional increase in LOS velocity dispersion is of order one. However, if the stellar initial mass function is bottom light, as it may be for UFD galaxies, then this value increase by half a dex. Our results apply to systems of populations of zero-age main-sequence stars rather than the populations of present-day red-giant branch (RGB) stars that have been studied previously in the context of dwarf-spheroidal galaxies.

370 Determining the extent of baryon-induced dark matter core creation: a first direct look at gravitational potential fluctuations

Understanding the response of dark matter to baryonic feedback is crucial before dwarf galaxy observations can be used to constrain dark matter particle physics. For the last decade, the stellar-to-halo mass ratio ($M_{\star}/M_{200}$) has been widely regarded as the single most important quantity in determining the expected effect of most baryonic feedback models on cold dark matter halos at $z=0$. In this talk, I will present results from the EDGE2 state-of-the-art radiation-hydrodynamical simulations that suggest that $M_{\star}/M_{200}$ ratio is only partially correlated with dark matter core formation. I will show that the dark matter density at $z=0$ is highly sensitive to the specific formation history of a galaxy, and introduce a new quantity that can be used to accurately predict the impact of baryonic feedback on dark matter halos (Muni et al 2024). I will also present a new technique, first of its kind, to examine variations in the gravitational potential at the centres of EDGE halos on timescales shorter than their dynamical time (< 5 Myr). I will provide evidence that these potential fluctuations are directly driven by supernova feedback and discuss their correlation with the presence of cores (Muni et al in prep 2025).

Speaker: Claudia Muni (Durham University)

371 Dark Subhaloes in dwarf spheroidal galaxies

One of the strongest predictions from the Cold Dark Matter (CDM) paradigm is the existence of a very large number of subhaloes that do not form in-situ stars (i.e. `dark'). Dwarf spheroidal galaxies (dSphs), being the most dark matter-dominated galaxies in the universe, provide a unique laboratory for testing these theories.
In this talk I will show that dSphs are particularly sensitive to perturbations from dark subhaloes owing to their low velocity dispersions and high phase-space densities. I will present N-body experiments that show how CDM subhaloes orbiting in dSphs can have a significant impact on the internal dynamics of these galaxies and induce secular evolution. In particular, self-graviating subhaloes generate a fluctuating gravitational field that injects energy into stellar orbits, causing a gradual expansion of dSphs in their CDM haloes.

372 A detailed characterisation of low-mass dark matter subhalo tidal tracks via numerical simulations

In this work, we perform a suite of numerical simulations specifically designed to analyse the evolution of the circular velocity peaks ($V_\mathrm{max}$, and its radial value $r_\mathrm{max}$) of low-mass DM subhaloes due to tidal stripping. To perform this task, we have employed the improved version of the DASH library, introduced in our previous work Aguirre-Santaella et al. (2023) to study subhalo survival.
More specifically, we follow the tidal evolution of a single DM subhalo orbiting a Milky Way (MW)-size halo, the latter with a baryonic disc and a bulge replicating the actual mass distribution of the MW. We simulate subhaloes with unprecedented accuracy, varying their initial mass, concentration, orbital parameters and inner slope (NFW and prompt cusps are considered). We also consider the effect of the time-evolving gravitational potential of the MW itself.
Here, we also broaden our vision with respect to previous literature not just characterizing tidal tracks at the apocentres, but exploring the pericentres as well. Several important discrepancies arise, especially with respect to works that do not account for baryonic material inside the host.
In general, $r_\mathrm{max}$ shrinks more than $V_\mathrm{max}$, leading to a continuous rise of subhalo concentration with time. The velocity concentration at present is found to be up to two orders of magnitude higher than the one at infall.
These findings significantly enhance our understanding of the dynamics and properties of low-mass DM subhaloes, providing valuable insights for future research, simulations and observations, as well as for indirect searches of DM.

373 The structural diversity of simulated and observed low-mass galaxy analogues

We compare the visual and structural properties of dwarf galaxies in ultra-deep HSC-SSP imaging of the COSMOS field with those measured from realistic HSC-like synthetic observations of dwarfs generated by two high-resolution cosmological hydrodynamical simulations - Illustris TNG50 and NewHorizon - using Sérsic profile fitting and non-parametric morphological metrics.

NewHorizon and TNG50 galaxies lie at opposite extremes of observed structural trends: NewHorizon produces diffuse, extended galaxies with shallow Sérsic indices, while TNG50 yields compact, concentrated systems with steep indices. Both simulations reproduce observed structural trends more closely at higher stellar masses (M* > 10^9.5 Msun) but fail to capture the full diversity of the observed COSMOS dwarfs at lower masses.

The distinct structural properties of NewHorizon and TNG50 galaxy populations reflect the underlying differences in their physical models, including ISM physics, star formation prescription and feedback implementation. The pronounced variations in the structural properties of simulated dwarfs in this mass regime underscores their heightened sensitivity to these processes. New observatories, such as the Vera C. Rubin Observatory and Euclid, will facilitate much more robust comparisons with simulations of low-mass galaxies, highlighting the utility of low-mass galaxies to constrain the physical mechanisms of galaxy formation and evolution and improve the galaxy evolution models implemented by simulations.

Speaker: Garreth Martin (University of Nottingham)

374 A Local Dwarf Galaxy Search and High-z Analogs

Since low-mass galaxies have experienced little merger history, they retain the remnants of the initial state of galaxy formation. Then low-mass galaxies provide the best laboratory for us to study the formation and evolution of galaxies and its associated dark matter haloes. At the same time, exploring the supermassive black hole (SMBH) at the center of the dwarf galaxy provides new clues for us to study galaxy-SMBH coevolution, galaxy feedback and quenching mechanism. And the study of the circumgalactic medium of dwarf galaxies is essential to understand the star formation activities. Using the DESI Image Legacy Survey data (g, r, z) combined with the WISE near-infrared survey data (W1, W2), I will present our machine learning model to search the dwarf galaxies (10^6 < M_*<10^9 M_⨀) in the local Universe (z < 0.02). The precision of separating dwarf galaxies from the contaminators could be as high as 95% and the recall could reach 76%. The verification using the independent data set, including DESI-EDR, SAGA and ELVES, shows excellent precision of > 96%. The late-type, ultra-low mass dwarf galaxies with high star formation rate might be analogs of galaxies at early Universe. Using DESI-DR1 data, we study its spectral and structural features. Further investigation finds that more than 200 of those local dwarf galaxy candidates have high x-ray emission fluxes, indicating possible existence of SMBH or IMBH.

Engaging the public with astronomy: what really works?

Organisers: Robert Massey, Andy Newsam, Lucinda Offer

40 years ago the Royal Society published its seminal report on what was then described as the “Public Understanding of Science”. Scientists moved first to public engagement, and more recently invited leadership from underserved communities, for example in the RAS 200: Sky and Earth and STFC Wonders schemes.

Few researchers now doubt the importance of public engagement. One slightly crude metric of its success is the popularity of astronomy undergraduate courses, with the number of students accepting places on these programmes growing from 581 in 2007 to 1795 in 2022.

On the other hand the field still has huge challenges in diversity. The 2023 Survey of the Demographics and Research Interests of the UK Astronomy and Geophysics Communities notes that women made up around 27% of lecturers in both astronomy and physics as a whole, for example, and just 4% of British academic staff were from minority ethnic groups.

So is it time to take a harder look at the effectiveness of the plethora of schemes to engage the ‘public’ with our science? Is the pressure for success preventing us from challenging ourselves to deliver change?

The session will include invited and contributed talks, and at least one panel discussion, thinking about how we can best draw on the incredible new astronomical facilities and space missions either under construction or expected to be operational in the years ahead.

This session will be organised by RAS staff and members of the RAS Education and Outreach Committee.

375 Engaging the public: getting to work

A look at some the tools, methodologies and the support available for those engaging the public with astronomy.
In this talk Adam Boal Public Engagement Officer at the Royal Astronomical Society will go through some of the steps to consider when your developing engagement activity. How to craft and tailor engagement activity to your audiences. Share top tips and how to avoid common engagement missteps. We will also look at what tools and support are out there to assist in planning and delivering astronomy engagement activity.

376 The Wynyard Planetarium: A 100% volunteer-operated outreach facility in the North East

Wynyard Planetarium and Observatory is located close to Stockton on Tees. This place exists since about 25 years and it was originally operated by paid staff within the local council. Due to a funding crisis the place had been threatened by closure, but local amateurs managed to take this place over after forming the TASC (Teesside Astronomical Science Centre) charity. This presentation describes the advantages and challenges met when operating a planetarium completely by volunteers.

377 The Jodcast: Opening Doors to Cutting-Edge Astrophysics

The Jodcast is the UK’s longest running (and one of the world’s longest running) astrophysics podcasts. The podcast has been produced by PhD students and staff from Jodrell Bank Centre for Astrophysics for nearly 20 years and currently reaches a monthly audience of approximately 900 listeners. Its success lies in making advanced concepts from cutting-edge astrophysics research more accessible to the wider public and offering an ‘open door’ to the world of academia. To broaden the reach of the Jodcast, we are now providing interview opportunities to early career researchers through our Jodbite series, reaching out to younger audiences through social media engagement (as well as putting faces to voices) and producing live recording events such as Jodcast Live! At The Pint of Science. Overall, the Jodcast demonstrates that science communication can be pitched at multiple levels to bridge the gap between the public and academia and provides a platform to access the most exciting upcoming research in astrophysics.

378 Discs, Stars, Nebulae and...Aliens? A 3D Exploration of Spiral Galaxies!

In astronomy outreach, 2D visual aids are traditionally used to explain astronomical topics, but these can fail to effectively convey complex ideas and engage a young audience. To address this, we created an interactive workshop series for under-served lower secondary school children (ages 11-14) in South Wales to explain star formation using 3D films. The visuals of our films are generated using a combination of standard 2D simulation videos and telescope images, which an adaption of a stereoscopic effect called “anaglyph” is applied then to. This effect creates and combines cyan/red filtered versions of a 2D image, to produce a 3D image, when viewed with dual cyan/red lensed glasses. Using this setup our audience visits a nearby spiral galaxy, zooms thorough it and visits various astronomical objects (stars, nebulae, planets) where the science of these is explained. Here we showcase part of our film, demonstrate how the educators can easily make and incorporate anaglyphs into their own talks, and present the feedback we’ve received so far.

379 Astronomy through the Herschels: Inspiring Inclusion through Science and Storytelling

The Astronomy through the Herschels workshops foster social inclusion and raise aspirations, particularly among Wonder Communities—those who may feel science isn’t for them or who have historically lacked equitable access to STEM opportunities. Part of the Explore Your Universe – Valuing Inclusion project, supported by ASDC and STFC, the programme focused on three outcomes: developing a sense of possible selves, acquiring new skills, and building social connections.

Working with schools in low-socioeconomic areas, the workshops used the legacy of the Herschel family and their connection to Slough to spark curiosity and a sense of belonging in science. Children explored infrared and ultraviolet light, constellations, comets, and telescopes through creative sessions featuring actors portraying the Herschels, hands-on STEAM activities, links to STFC science and researchers, and the contemporary relevance of their work—such as the use of infrared in the James Webb Space Telescope.

The four workshops were:

• Connecting the Dots – An intro to the night sky combining constellations and simple circuits.
• William: The Telescope and Discovery Maker – How William Herschel’s curiosity led to tools, discoveries, and a science career.
• Caroline: The Comet Hunter – Caroline Herschel became a paid professional female astronomer and a Gold Medal winner.
• John: The Polymath Influencer – John Herschel’s inventive spirit, influence on science, and co-founding of the Royal Astronomical Society.

This session will share the design and delivery of the Astronomy through the Herschels workshops and highlight evaluation findings from the wider EYU programme, collected by ASDC.

Magnetic reconnection, topology and non-ideal instabilities

Organisers: Alexander Russell, Jonathan Eastwood, Gunnar Hornig, James McLaughlin, Christopher Prior, Julia Stawarz, Peter Wyper, Anthony Yeates

Magnetic reconnection is one of the most important processes in solar, space and astrophysical plasmas. In a highly conducting plasma with large length scales, magnetic field connections between plasma elements are conserved, allowing the accumulation of magnetic energy over time. However, conservation of connectivity can break down in small volumes – this has global consequences, for example enabling rapid conversion of magnetic energy in solar flares, auroral substorms and astrophysical jets and disks.

This session aims to bring together researchers working on magnetic reconnection, magnetic topology and resistive and collisionless instabilities, from the solar, space and astrophysics communities. Cross-cutting scientific discussions will cover theory, simulations, remote observations and in-situ observations.

Some of the key questions we are interested in addressing are:
o What do the latest numerical simulations and observations reveal about reconnection and non-ideal instabilities?
o How do recent new perspectives on topological properties, such as magnetic skeletons or helicity, shed light on dynamics such as flaring and coronal heating?
o How does turbulence affect reconnection, and vice-versa?
o How have results from the latest missions (e.g. Solar Orbiter and MMS), observatories (e.g. DKIST) and analysis tools (e.g. field line helicity) changed our understanding of these topics?

380 Reconnection between the interplanetary magnetic field and closed magnetotail structures

The Earth’s magnetotail is formed primarily of magnetic field lines that are topologically open, i.e. connected to the interplanetary magnetic field (IMF). During periods of northward-directed IMF, the magnetopause reconnection site moves tailward of the cusps, resulting in either the ‘stirring’ of magnetic flux without a net change in topology (“single lobe reconnection”), or the closure of the open magnetic flux that forms the magnetotail lobes (“dual lobe reconnection”). However, northward IMF is also favourable for the formation of a topologically closed structure in the magnetotail called a transpolar arc. We present direct observations of reconnection between the IMF and the magnetotail magnetic field close to a “wedge” of closed magnetotail field lines associated with a transpolar arc. When the lobe reconnection process is modified in this way, it leads to the opening of closed magnetotail flux associated with the transpolar arc. We also discuss the possible role of such a configuration in recently reported “non-lobe” high latitude reconnection events.

Speaker: Robert Fear (University of Southampton)

381 Multispacecraft Observations of Reconnection Topologies and Their Role in the Turbulent Energy Cascade

Energy transfer in magnetised plasmas is fundamentally shaped by the interplay between turbulence and reconnection. Coherent structures are central to intermittent magnetohydrodynamic turbulence, which is observed in situ in the solar wind. We establish a correspondence between the energy transfer rate and the magnetic topology of underlying turbulent fluctuations. Magnetic field topology is classified by the magnetic field gradient tensor, constructed from in situ observations by the four Cluster spacecraft forming a tetrahedron on a scale of ∼40 proton gyro-radii, and energy transfer rates are estimated from third-order structure functions. Energy transfer to decreasing scales, with positive transfer rates significantly larger than the mean, occurs preferentially in hyperbolic magnetic field topology, consistent with reconnection. Energy transfer to increasing scales, with large negative transfer rates, occurs preferentially in magnetic flux ropes. The forward and inverse MHD turbulent cascades are thus carried by current sheet fragmentation in reconnection and flux rope merging, respectively.

382 Identifying Magnetic Reconnection to Assess its Role in Collisionless Turbulent Plasmas using the Unsupervised Machine Learning TICC Algorithm

Within collisionless turbulent plasmas, intense thin current sheets can undergo magnetic reconnection, playing a crucial role in both turbulence dynamics and energy dissipation. The prevalence of magnetic reconnection may be influenced by the properties of the turbulent fluctuations in different environments. The Magnetospheric Multiscale mission (MMS) provides high-resolution, multi-point observations of Earth’s turbulent magnetosheath that are well suited for identifying turbulence-driven magnetic reconnection. However, identifying magnetic reconnection sites is challenging and time-consuming due to the range of scales and complex magnetic field topologies involved. We aim to systematically identify magnetic reconnection events in turbulent plasma observations using an unsupervised Machine Learning (ML) algorithm, Toeplitz Inverse Covariance-Based Clustering (TICC). This method requires key physical features that highlight magnetic reconnection sites as input. TICC clusters timeseries data by modelling each cluster as a time-invariant correlation network, enabling the detection of complex patterns within turbulence. The ability of the method to identify magnetic reconnection events is evaluated against existing datasets of turbulence-driven reconnection. Once an optimal model is established and the cluster corresponding to reconnection sites is identified, the occurrence rate of reconnection is quantified across different turbulent intervals and compared with bulk properties to understand factors controlling its prevalence. Then, the model will be applied to a broader range of turbulent datasets to support preliminary results that suggest a link between reconnection and turbulence parameters such as correlation length and energy dissipation. This study aims to provide key insight into how the role of turbulent plasmas may vary across different turbulent environments.

383 Estimating the Contribution from Small-Scale Terms in the Generalised Ohm’s Law to the total Electric field.

Magnetic reconnection and plasma turbulence are deeply interlinked processes. The turbulent evolution of magnetic structures lead to the onset of reconnection events and turbulence is present in different regions associated with the reconnection dynamics, e.g., inflow region, exhaust, Ion diffusion region and Electron diffusion region. Plasma turbulence plays a fundamental role because it transports energy across spatial scales from the large energy injection scales down to small-scales at which energy is dissipated. A key challenge is understanding how the small-scale turbulent dynamics couple into and influences the large-scale behaviour of the system, this is particularly important to assess the importance of anomalous effects on the reconnection dynamics. In this work we tackle this challenge using Vlasov-Hybrid and fully kinetic Paritcle-in-Cell (PIC) simulations modelling conditions similar to the turbulence in Earth’s magnetosheath and employing a scale filtering analysis to estimate the contribution from small-scale terms in the generalised Ohm’s law, such as the anomalous transport and anomalous resistivity, to the total electric field. We also establish the dependence of the small-scale terms on large-scale quantities such as the mean magnetic field, mean current density and mean plasma vorticity. This is highly relevant to produce Sub-Grid-Scale (SGS) models that can be used to perform Large-Eddy-Simulations (LES) of plasma turbulence and magnetic reconnection in astrophysical systems where the plasma conditions make it unfeasible to perform direct numerical simulations due to the scale separation between the system size scale and the dissipation scale.

384 On field line slippage rates in the solar corona

Magnetic reconnection is one of the fundamental dynamical processes in the solar corona. The method of studying reconnection in active region-scale magnetic fields generally depends on non-local methods (i.e. requiring information across the magnetic field under study) of magnetic topology, such as separatrix skeletons and quasi-separatrix layers. The theory of General Magnetic Reconnection is also non-local, in that its measure of the reconnection rate depends on determining the maxima of integrals along field lines. Here, we complement the above approaches by introducing a local theory of magnetic reconnection, that is one in which information about reconnection at a particular location depends only on quantities at that location. The theory connects the concept of the field line slippage rate, relative to ideal motion, to the underlying local geometry of the magnetic field characterized in terms of the Lorentz force and field-aligned current density. The theory is adaptable to the inclusion of different forms of non-ideal physics and relevant quantities, e.g. reconnection rates, are simple and fast to compute. Related to the last point, the theory can be easily computed in both simulations and magnetic field extrapolations and provide extra information that is not available from non-local theories. We present some illustrative examples.

ENGAGING WITH INDUSTRY

Organisers: Ariadna Calcines Rosario, Nazim Ali Bharmal, Deborah Malone

This parallel session aims to promote interactions between scientists and industry and provide a platform for NAM exhibitors.

Synergies between academia and industry is a key factor in the development of projects in the astronomy and space sectors. We encourage interactions from the scientific and design side, discussing ideas and specifications for the current and future projects, and companies, presenting their capabilities and evaluating the feasibility of those ideas. We encourage attendees at all career stages, both from Academia and Industry, to participate and discuss ideas on how to work together better as a team so the technology developments meet the specifications of the next generation of instruments and vice versa, as well as discussing available resources and opportunities to make this happen.

The exhibitor presentations are chaired by Ariadna Calcines Rosario, Head of Optical Design, Centre for Advanced Instrumentation, Durham University.

The panel session is chaired by Carol Watts, UK Industrial Liaison Officer for ESO and SKAO at STFC UKRI.

Panel members:

William Humphreys, UK Space Agency, Senior Programme Manager
Paula Chadwick, Durham University, Head of the Physics Department
Óscar González, UK Astronomy Technology Centre, Senior Project Scientist
Chris Howell - Durham University, Senior Business Development Manager

385 Invited Talk by Carol Watts, STFC UKRI: Astronomy opportunities with international science facilities, and facilitating academic and industry engagement

Opening talk by Carol Watts from STFC UKRI

386 Invited Talk: "The UK Space Agency and Astronomy"

Invited talk by William Humphreys, UK Space Agency

09:20 Exhibitor Presentations

Conference Exhibitors will be given an opportunity to talk about their institutions/ companies.

09:50 Q&A for Exhibitors or Speakers

Q&A with Exhibitors and/or speakers.

10:05 Panel discussion

A discussion with the members of the panel on the development of Astronomical instrumentation and Industry.

Panel Members:
William Humphreys, UK Space Agency, Senior Programme Manager
Paula Chadwick, Durham University, Head of the Physics Department
Óscar González, UK Astronomy Technology Centre, Senior Project Scientist
Chris Howell - Durham University, Senior Business Development Manager

10:25 Final remarks

10:30 Coffee Break

11:00 Annoucements

Plenaries 4 - Thursday

387 Solar Particle Acceleration and Transport

The Sun is the most powerful particle accelerator in our solar system, releasing up to 1025 joules of energy during explosive events known as solar flares. In the solar corona, electrons and ions are accelerated to nearly the speed of light, either descending into the dense solar atmosphere or escaping into interplanetary space. Despite our close proximity to the Sun and the extensive data gathered from ground and space-based telescopes for more than 80 years, numerous questions remain about the physics of solar particle acceleration and the mechanisms by which these particles transfer their energy to the plasma in the solar system. This presentation will give an overview of solar particle acceleration and transport, highlighting our current understanding and identifying its limitations, discussing the astrophysical analogue, and exploring how new solar instrumentation will usher in a new era of insight.

Speaker: Hamish Reid (University College London)

388 LGBTQIA+ inclusion in astronomy

The 2019 Physical Sciences Climate Survey was the first investigation of the working, teaching and studying climate for LGBT+ physicists, astronomers and chemists in the UK. This study brought into stark focus the isolation, exclusion and outright discrimination faced by individuals with minority sexual orientations, gender identities that lie outside of the societal model which classifies humans into binary categories that a person always, solely and completely identifies with, and intersex traits/variations in sex characteristics. In this talk, I'll present an overview of the current international picture of LGBTQIA+ rights and freedoms, highlight results from studies into barriers to LGBTQIA+ inclusion across the sciences, and celebrate the work being done by a variety of groups to support LGBTQIA+ astronomers.

Speaker: Dr Claire Davies (University of Exeter)

12:45 Lunch

Early Career Lunch and RAS ECN Town Hall

Organiser: RAS Early-Career Network, Matthew Temple, Marieta Valdivia Lefort

During this lunch session, Early Career Researchers (ECRs) will have the opportunity to meet in person, network, and learn more about the RAS Early-Career Network. Previous NAM lunch sessions have provided a popular forum for ECRs to network and access informal peer-support. Given that many PhD students and postdocs can feel isolated within larger physics departments, this networking lunch aims to provide not only a social space for ECRs but also a sense of community, and to give delegates a chance to meet fellow Astronomy & Geophysics researchers and, for new PhD students, their nationwide PhD cohort.

This session is organised by the Early Career Network (ECN) of the RAS. It will also provide an informal ‘town hall’ space for Early Career Researchers to meet the RAS ECN and express their concerns and opinions about the current challenges facing PhD students and postdocs. At the same time, speakers from the “Jobs in Astronomy and Geophysics” session will be present to answer questions and provide advice in a more informal setting.

STFC Astronomy Grants Panel Community Session

Organisers: Kim Burchell, Jenny Hiscock, Mark Sullivan, Mark Swinbank, Chloe Woodcock

The STFC Astronomy Grants Panel (AGP) funding schemes are the primary source of support research in astronomy, astrophysics, solar system, and planetary science in the UK. This session will provide an overview of the Small Award and Large Award funding routes, and provide details on the general outcomes of the schemes following their implementation in 2023. This session is an opportunity for the community to give feedback on the new schemes, and participate in a question and answer session with the STFC Astronomy Team and the AGP Chairs. This session is designed for all prospective applicants, whether new to the schemes or experienced.

Revealing the Milky Way Ecosystem with GaiaNIR (GaiaNIR)

Organiser: Nicholas Walton; co organiser: Vasily Belokurov, Cathie Clarke, Alis Deason, Victor Debattista, Denis Erkal, Andreea Font, Daisuke Kawata, John Magorrian, Jason Sanders, Vicky Scowcroft

The ESA Gaia 3-D map of over two billion stars in our Milky Way (MW) coupled with community-powered research is both challenging and refining our understanding of the complex, interlinked processes governing the formation and evolution of the MW.

Next generation near infrared astrometry has been identified through the ESA Voyage 2050 process as a candidate ESA Large (L5) mission. Building on Gaia heritage, the GaiaNIR mission will probe the Milky Way’s hidden regions, enabling a comprehensive understanding of galaxy formation across time.

The lunch session will include an update on the GaiaNIR mission (from the GaiaNIR PI, David Hobbs, Lund). It will include talks detailing GaiaNIR’s prime science goals, for example showing how its survey of some 15 Billion sources concentrated in the inner regions of the MW, un-surveyed by Gaia but transparent to GaiaNIR, will untangle the complex interplay of the MW ecosystem. This revealing, for example, how the oldest stellar population at the heart of the MW affected the development of its disc structure seen today. The baseline design for the instruments on GaiaNIR will be presented, noting significant recent developments (driven from the UK) in nearIR detectors, which in turn opens the possibility for a wider range of instrument capabilities.

The opportunity for UK researchers to become involved in developing the case, scientific and technical, for GaiaNIR, through the nascent GaiaNIR:UK group, will be highlighted. This timely as planning for GaiaNIR is accelerating, with key decisions to be taken in the next few years.

14:15 STFC community session*

Prof Michele Dougherty (STFC executive chair)
Prof Grahame Blair (STFC executive director of programmes)
Dr Caroline Harper (Head of space science, UKSA)

15:45 Coffee Break

Radio Astronomy in the build up to the SKAO

Organisers: Johannes Allotey, Emmy Escott, Catherine Hale, James McGarry, Lucy Oswald, David Williams-Baldwin

The field of radio astronomy will soon be revolutionised by the arrival of the Square Kilometre Array telescopes. Now that the first fringes have been recorded with SKA-Low, and the first SKA-Mid dish is in place, it is time to look to the future of radio astronomy and the scientific opportunities coming up, and to reflect on the state-of-the-art science with precursor/pathfinder telescopes.

The goal of this session is to showcase the breadth of work conducted with SKA precursor and pathfinder instruments, such as e-MERLIN, MeerKAT and LOFAR across a diverse range of science goals, and to provide an opportunity for discussion and connection over plans for future science with the SKA Observatory (SKAO). We also will likely include discussion from invited speakers to update on the SKAO and the Science Regional Centres.

The session will be organised and led by members of the SKAO UK Early Career Researcher (ECR) committee, and will build on the success of the equivalent session at NAM2023.

389 Discovery of the largest radio jet at z ~ 5 in the radio-loud quasar J1601+3102

We present the discovery of a >66 kpc radio jet in the radio-loud quasar J1601+3102, residing at a spectroscopically confirmed redshift of z = 4.912. This makes it the largest projected radio jet known to date at such early times. Using the International LOFAR Telescope, two apparently unrelated "companion sources" have been spatially resolved into two radio lobes. Spectroscopic follow-up with Gemini North confirmed the redshift which allowed a physical size to be derived. Such large jets have been argued to be elusive due to the high inverse-Compton scattering losses in the Early Universe. From the Gemini/GNIRS rest-frame-UV spectrum, a black hole mass of 4.5 × 10^8 solar masses and Eddington luminosity ratio of 0.45 are derived. This black hole mass is relatively low compared to the known high-z quasar population. A high Eddington ratio is not immediately associated with stable jet launching either. Can powerful jets be launched from lower black hole masses? Is J1601+3102 an exception, or the tip of an iceberg of large jetted AGNs at high redshifts that we have been missing hitherto? With sensitive SKA-like instruments we can now start searching for these objects to better understand the formation and evolution of jetted radio sources in the Early Universe. This discovery would not have been possible without the ILT, highlighting the need for the next-generation of (low-frequency) radio telescopes.

Speaker: Frits Sweijen (Durham University)

390 The alignment of galaxies and AGN jets in the cosmic web environment probed with LOFAR

Active galactic nuclei (AGN) play a crucial role in the evolution of massive galaxies, but their fueling and feedback efficiency depend on the environment. In this talk, I will present a statistical study of the orientations of AGN jets and their optical counterpart in relation to the cosmic web environment, leveraging data from the Low-Frequency Array (LOFAR). Using LOFAR Two-metre Sky Survey (LoTSS), DESI Legacy Imaging Surveys, and the SDSS cosmic filament catalogue, we find that galaxy optical major axes tend to align with cosmic filaments, suggesting the growth of galaxies through mergers along filaments. On the other hand, AGN jets, typically perpendicular to the host galaxy’s major axis, show more randomized orientations in cosmic filament environments. This supports a scenario where black holes in filament galaxies experience chaotic accretion as a result of numerous mergers. I will discuss the implications of these results in terms of the large-scale alignment of radio jets, intrinsic alignment of galaxies, and anisotropic quenching of satellite galaxies. The SKA will enable deeper studies of AGN populations over a large cosmic volume covering a range of cosmic environments, revealing how the large-scale structure influences black hole growth and AGN feedback. This study highlights the potential of the SKA to further unravel the connection between AGN and the cosmic web.

391 Probing M Dwarf Magnetism with e-MERLIN and VLA: A Step Toward the SKA Era

Radio activity in low-mass stars, including M dwarfs and substellar objects, has gained significant attention over the past decade. This interest has been driven in part by SKA pathfinder telescopes, particularly LOFAR, which have provided critical insights into the radio properties of stellar/sub-stellar objects at meter wavelengths. The upcoming Square Kilometre Array (SKA) is poised to revolutionize our understanding of magnetic activity in these objects by offering unprecedented sensitivity and frequency coverage, enabling the detection of weak, persistent emission from a broader range of substellar sources. Meanwhile, the James Webb Space Telescope (JWST) has recently identified numerous L, T, and Y dwarfs, providing an unprecedented window into their atmospheric properties. Together, SKA and JWST will offer a complementary view of ultracool dwarfs, probing both their magnetic fields and atmospheric structures.

We present the detection of an M dwarf using e-MERLIN in conjunction with the Very Large Array (VLA), further demonstrating the growing importance of high-sensitivity radio interferometers in studying magnetism in these objects. Here, we discuss this new detection and its implications for our understanding of magnetic activity in low-mass stars.

392 MIGHTEE-HI: The radial acceleration relation with resolved stellar mass measurements over 1 Gyr

The radial acceleration relation (RAR) is a fundamental relation linking baryonic and dark matter in disc galaxies through the observed acceleration derived from dynamics to the one estimated from the baryonic mass. Notably, this relation exhibits small scatter, thus providing key constraints for models of galaxy formation and evolution, by essentially allowing us to map the distribution of dark matter in galaxies. However, it has only been extensively studied in the very local Universe.
In this talk, I present new measurements of the RAR, utilising a homogeneous, unbiased sample of HI-selected galaxies from the MeerKAT International Tiered Extragalactic Exploration (MIGHTEE) survey.
I introduce a novel approach of resolved stellar mass modelling from spectral energy distribution (SED) fitting across 10 photometric bands to determine the resolved mass-to-light ratio, which is essential for measuring the baryonic acceleration, as opposed to relying on a fixed mass-to-light ratio.
Our findings show that the stellar mass-to-light ratio varies across galaxies and radially. The results suggest that the RAR in this sample favours lower mass-to-light ratios compared to previous studies. I find that adopting a spatially varying mass-to-light ratio yields the tightest RAR with an intrinsic scatter of only 0.04 ± 0.02 dex.
I will address the implications of these findings for the fundamental nature of RAR. The results highlight the importance of resolved stellar mass measurements in accurately characterising the baryonic contribution to the rotation curve and in providing constraints to break the disk-halo degeneracy, opening exciting prospects in future studies with upcoming HI surveys.

Speaker: Andreea Varasteanu (Oxford University)

393 Mapping Faraday Rotation in Large Radio Galaxies from POSSUM

We report the largest study to date of the resolved Faraday rotation (RM) and depolarization across the lobes of double radio sources. Our work utilises the ongoing EMU and POSSUM surveys with ASKAP, which will cover half the sky. EMU produces broad-band Stokes I images and a source catalogue at 943 MHz. POSSUM performs RM synthesis on the same data, yielding RMs at each high-SNR pixel.

POSSUM will measure RMs for ~1 million sources with many thousands large enough to resolve details within each radio lobe. This allows us to check claims for systematic RM patterns such as the Laing-Garrington effect, which rest on only a few dozen objects, with poorer data than POSSUM will achieve for thousands. Pre-POSSUM results were usually explained in terms of the inclination of a source embedded in an atmosphere that dominates the Faraday depth, but this may be too simple.

As a prototype, we used a 0.05 sr region where RM maps and EMU catalogues have been made. We selected about 125 'islands' with solid angle > 6000 sq" above the 5-sigma Stokes I contour. Most represent a single source but some constitute one lobe of a double, while others are superpositions of unrelated objects. Selection by size yields a lower mean luminosity than by flux density- Fanaroff-Riley type I sources are common, typically found in groups/clusters. We present highlights from these maps, an analysis of a subset to see how much human quality control is needed, and a first look at statistical trends.

Speaker: Sam Venables (Jodrell Bank Centre for Astrophysics, University of Manchester)

394 Looking Beyond Linear Scales with HI Intensity Mapping

In the late Universe, neutral hydrogen (HI) is found inside dark matter haloes hosting galaxies. Using a technique called intensity mapping, the distribution of HI can be used as a tracer for large-scale structures. The accessible scales from the data depend on the instrument used, i.e. single dish telescope or interferometer. Radio interferometers are sensitive to scales that simultaneously probe large-scale structure cosmology and local astrophysics. Thus, interferometric HI intensity mapping surveys can simultaneously constrain astrophysical and cosmological parameters. The advent of the SKAO precursor MeerKAT has started producing surveys with sufficient sensitivity to statistically probe this gas in galaxies. I will present the results of HI intensity mapping at low redshift (z<0.5) using MeerKAT surveys. These results directly affect the expectation from SKAO since the data emulates many of the challenges imminent for SKA-mid data. I will discuss the new methodologies we have developed for intensity mapping. This led to the first detection of the HI auto-correlation power spectrum at z<0.5 with a high statistical significance and constraints on the abundance and distribution of HI. I will also discuss our efforts to combine multi-pointing interferometric surveys for intensity mapping. The techniques developed have led to the first upper limits on the HI auto-correlation power spectrum from the MIGHTEE survey. Finally, I will show the prospects of intensity mapping with the SKAO using the lessons learned from the precursor data.

395 Why are the radio sources missing in the Fornax cluster?

Recently, the ASKAP POSSUM and MeerKAT surveys revealed an apparent lack of radio source counts in the Fornax galaxy cluster field. The sources in this patch of sky also appeared to be less polarised. These observations are peculiar and could be important signatures of depolarisation on galaxy cluster scales. In this work, we quantified the effects on polarisation of radio point sources behind a large-scale intracluster shock. Our ray-tracing calculations revealed that, generally, bright sources do not experience any significant changes in polarisation, whereas faint sources either get severely depolarised or enhanced as their radiation propagates through the intracluster medium. Notably, most of the dim sources behind the shock gain linear polarisation. This is because the gas and magnetic fields are highly compressed within the shock, causing it to be more linearly polarised than the surrounding medium. We also carried out a magnetohydrodynamic FLASH simulation of an in-falling subcluster into a main cluster and found a substantial increase in the local Faraday rotation measures behind the shock front. These effects would impact the interpretations of radio observations, particularly with SKA-Low, where the polarisation bias in faint sources must be corrected for in the statistical analyses of dense rotation measure grids.

Speaker: Dr Alvina Yee Lian On (National Center for Theoretical Sciences, National Tsing Hua University)

17:39 Update from SKA ECR committee

Barred Galaxies: Unravelling Their Evolution, Dynamics and Cosmic Role

Organiser: Zoe Le Conte; co organisers: Alex Merrow, Rebecca Smethurst, Thomas Tomlinson

Our understanding of bar formation, evolution, and their interactions with host galaxies is rapidly advancing, revealing new insights into their role in galaxy evolution. Bars are among the most common features in disc galaxies, present in over two-thirds of local spirals, and they influence their hosts by redistributing angular momentum, triggering gas inflows that fuel star formation and potentially feed AGN. Bars also reshape stellar orbits within the galaxy, including the inner regions, outer discs, and stellar halos.

Recent observations from high-resolution surveys like the HST and JWST have provided unprecedented insights into bar-driven evolution across environments and redshifts. Integral field units such as MUSE offer critical data on stellar populations, stellar and gas kinematics, bar-driven star formation and AGN activity, while Gaia enables a star-by-star analysis in the Milky Way.

Simulations complement these advances by modelling barred galaxies with increasing resolution, allowing for detailed studies from high redshifts to the present. These simulations help interpret observational data and improve understanding of stellar chemical evolution and accretion processes, thus facilitating a more accurate interpretation of observational data.

This session will address the still outstanding questions about bar formation, environmental influences on galaxy stability, the kinematics of bars, the role of bars in triggering and fuelling AGN, and bar-driven evolution within dark matter halos. We will discuss how combining high-resolution photometric surveys with cosmological simulations can bridge theory and observations, and how upcoming facilities like MOONS, BlueMUSE, MAVIS, SKA, and ELT will enhance our understanding of galaxy dynamics.

396 Automated Bar and Spiral Arm Segmentation using Deep Learning

Identifying the extent of internal galaxy structures can be incredibly helpful in unravelling their evolutionary histories. For bars in particular this can allow for precise measurements of colour, stellar mass, bar length and alignment with the disk. We present ZooBot:3D, a deep learning model trained using the volunteer classifications from the Galaxy Zoo: 3D project, capable of generating highly detailed segmentation maps of disk galaxies. We employ this model to produce maps for ~500,000 galaxies in the DESI Legacy Survey and demonstrate how these masks can be used to study the intricate properties of barred and unbarred spirals. Finally, we will detail the forthcoming public data release of these segmentation products and lay out plans for future work in this area.

Speaker: Ashley Spindler (University of Hertfordshire)

397 Tracing galaxy morphology and evolution with autoencoders

Representation learning allows astronomers to uncover relationships between galaxies by using the learned feature space of deep learning models. This space learns the physical appearance of galaxies, with galaxies of a similar appearance occupying a similar region in the feature space. As the appearance of galaxies is strongly affected by their morphology, we can use the feature space to find galaxies with a similar appearance, and therefore, morphology. This is important as galaxies with a similar morphology and mass likely share similar evolutionary histories. Using these principles, I will demonstrate how we can use the feature space to trace the evolutionary history of galaxies at low redshift, out to a redshift of z~1.

Using data from the IllustrisTNG-50 simulation, we select galaxies at low redshifts and find pseudo-progenitors at higher redshifts. These pseudo-progenitors are galaxies with similar properties (e.g. stellar mass, size, star formation rate) to the real progenitors of the low-redshift galaxies (i.e. when the low-redshift galaxies were at an earlier evolutionary stage, at higher redshift). Because of these shared properties, these pseudo-progenitors are likely analogues for the low redshift galaxies at earlier stages of their evolutionary history. Thus, the pseudo-progenitors could evolve into galaxies with similar properties and morphologies to the selected galaxies at low-redshift. This means that we are able to trace galaxy morphology and evolution with high accuracy, the next steps for this process are to test this method with real observational data and uncover the properties of progenitor populations for galaxies of particular morphological types.

398 MUSE view of gas inflows in nearby galaxies: Connections to Nuclear Activity and Central Morphology

Gas inflows shape galaxy evolution by enhancing star formation (SF), forming nuclear rings/discs, and fuelling AGNs, which trigger outflows and cause quenching. Understanding the mechanisms driving inflows to galactic nuclei is therefore crucial. One well-established mechanism causing gas inflows is bar-driven extended shocks, which manifest as coherent velocity jumps in kinematic maps. Despite extensive research, whether the dominant mechanism of gas inflows to galactic nuclei is analogous to extended shocks in bars remains unclear. Using MUSE, we searched for extended shocks in gas kinematics of 21 nearby galaxies. We find a lower limit of 52% in our sample exhibiting extended shocks within their 1 kiloparsec, all occurring in barred galaxies. Unbarred galaxies lack extended shocks, which implies the critical role of bars in facilitating gas inflows to the galactic nuclei. Investigating how extended shocks relate to dominant nuclear activity, we show that while the presence of nuclear bars is linked to AGN activity, in their absence, inflow primarily fuels SF. Further we correlate the extended shock characteristics and the presence of nuclear bars and rings in our sample. A strong correlation emerges between presence of extended shocks and nuclear rings, supporting the role of gas inflows in nuclear ring formation. Our study supports extended shocks as a dominant mechanism for nuclear gas inflows, shaping central morphology and driving nuclear activity.

399 Effects of bar to the dynamics in the Galactic disc

It has been demonstrated in many simulations that secular evolution driven by non-axisymmetric structures is crucial to the evolution of disc galaxies. The Galactic bar, as a dominant non-axisymmetric structure in many disc galaxies, has been studied intensively in simulations. With Gaia DR3, we can now begin to study the imprints that the Galactic bar has left on the Milky Way disc to test previous results obtained from simulations. In this talk, I will discuss the time-resolved picture of both the inner and outer Milky Way disc and their correlation with bar-driven secular evolution

In the inner disc, we map the chrono-kinematic evolution using Mira variables. We see evidence that bar-like kinematics exists ubiquitously in all stellar populations younger than 11 Gyr, significantly older than the estimated age of the Galactic bar, and that younger stars exhibit stronger bar signatures. This is a consequence of the kinematic fragmentation, where all disc populations can be trapped into bar-like orbits in a barred potential, and kinematically colder populations respond more effectively to the galactic bar.

In the outer disc, we present evidence of radial migration driven by corotation resonance dragging from a slowing bar, a star dragged from the inner to the outer disc by the expansion of the corotation radius. We show that the expected age–metallicity pattern and its spatial dependence from this mechanism closely match observations. Furthermore, we constrain the pattern speed history of the Galactic bar, assuming this mechanism dominates the radial migration processes in the Milky Way’s disc.

400 Stellar Populations in Galactic Bars with Machine Learning

Galactic bars play a crucial role in the evolution of disk galaxies, influencing gas dynamics, star formation, and secular evolution. However, identifying bars in a large sample of galaxies has been challenging. Our understanding of the impact of bars has leaped forward with Galaxy Zoo 3D: a citizen science project aimed at identifying bars in thousands of galaxies.

In this work, we use a machine learning model trained to identify bars in optical ground-based data to look at bars across a much larger sample. We leverage the imaging of almost 100,000 galaxies in the UNIONS survey and identify weak and strong bars within them. Using Spectral Energy Distribution fitting, we compare the stellar populations inside and outside the bar, to trace the influence of the bar on the stellar dynamics and star formation. Our results provide new insights into the role of bars in shaping galaxy evolution, whilst also demonstrating the power of machine learning in large-scale extragalactic studies.

Speaker: Elizaveta Sazonova (University of Waterloo)

401 A stellar mass-dependent phase transition in disc galaxies

Bars have been active and key actors in secular evolution, gas re-distribution and star formation in disc galaxies for at least 10 Gyr. While bars have been extensively studied via observations, models and simulations, we still do not know or even understand how those emerging tumbling structures truly impact the building and evolution of structures.
We have recently provided new strong evidence for a physically motivated change of regime between low and high-mass galaxies based on a unique grid of hydro-dynamical simulations and an exquisite multi-wavelength dataset (HST, JWST, MUSE/VLT, ALMA, Astrosat, VLA, Meerkat).
In this talk, I will illustrate those results by demonstrating how central mass concentrations build up via bar-driven inflows, how star formation can be either prevented or boosted and how it depends on relative locations within the disk, and how the stellar mass dependent phase transition emerges from the relative balance between feedback and gravity. I will provide a holistic view of such processes (including a connection to our Milky Way), leveraging on our simulations and observations (specifically focusing on ALMA, JWST and HST), further emphasising their important influence on the evolution of discs since their advent, something that may not usually be captured or considered in cosmological context studies.

Gamma-ray Bursts and their contribution to multi-messenger astronomy, cosmology, and the cosmic star-formation rate

Organiser: Gavin Lamb; co organiser: Kendall Ackley, Dimple, Ben Gompertz, Nusrin Habeeb, Shiho Kobayashi, Joe Lyman, Soheb Mandhai, Conor Omand, Patricia Schady, Nial Tanvir

Gamma-ray bursts are shining beacons that mark the moment of black-hole formation following the violent core-collapse of massive-stars, and the gravitational-wave-driven mergers of neutron-star binaries. The electromagnetic observations of gamma-ray bursts and their accompanying transients (the afterglow and supernova or kilonova) continue to reveal unexpected phenomenology, and generate new questions, some of which multi-messenger probes will answer. One such example is the long held assumption that the population-level bimodality of observed burst-duration clearly indicates the gamma-ray burst progenitor. This has been spectacularly cast in doubt following the discovery of kilonovae (merger origin) following two long-duration gamma-ray bursts (classically assumed to be core-collapse supernovae), GRB211211A and GRB230307A – where JWST observations of the latter, were crucial in determining the merger origin. These transient events originate in extreme astrophysical environments where: heavy elements are synthesised (r-process nucleosynthesis) and thrown out to enrich their host-galaxy (see GRB230307A); space-time is twisted and highly curved (Kerr metric), relativistic jets are launched and matter is accelerated to > 99.995% the speed of light; ionising radiation is emitted in beams from host galaxies out to, at least, z~9.4 (see GRB090429B), within or before the era of reionization; gravitational-waves are combined with highly luminous electromagnetic signals (GRB170817A); and the ideal conditions (large energy densities and magnetic fields, relativistic shocks, neutrino winds, particle acceleration etc.) for astro-particle experiments.

This session will highlight new observations, theory, modelling developments for gamma-ray bursts and related multi-messenger transients, their influence on their environments, and the discovery potential of new and upcoming instruments.

402 Multi-Peaked Non-Thermal Light Curves from Magnetar-Powered Gamma-Ray Bursts

Binary neutron star mergers and collapsing massive stars can both create millisecond magnetars. Such magnetars are candidate engines to power gamma-ray bursts (GRBs). The non-thermal light curve of the resulting transients can exhibit multiple components, including: the GRB afterglow, pulsar wind nebula (PWN), and ejecta afterglow. We derive the timescales for the peak of each component and show that the PWN is detectable at radio frequencies, dominating the emission for $\sim$ 6 years for supernova/long GRBs (SN/LGRBs) and $\sim$ 100 days for kilonova/short GRBs (KN/SGRBs) at 1 GHz, and $\sim$ 1 year for SN/LGRBs and $\sim$ 15 days for KN/SGRBs at 100 GHz. The PWN emission has an exponential, frequency-dependent rise to peak that cannot be replicated by an ejecta afterglow. We show that PWNe in SN/LGRBs can be detected out to $z \sim 0.06$ with current instruments and $z \sim 0.3$ with next-generation instruments and PWNe in KN/SGRBs can be detected out to $z \sim 0.3$ with current instruments and $z \sim 1.5$ with next-generation instruments. We find that the optimal strategy for detecting PWNe in these systems is a multi-band, high cadence radio follow-up of nearby KN/SGRBs with an x-ray plateau or extended prompt emission from 10 -- 100 days post-burst.

403 EP250108a/SN 2025kg : the kangaroo’s first hop and its implications for gamma-ray bursts and fast X-ray transients

Einstein Probe has opened a new window into X-ray transients, particularly the diverse sample of fast X-ray transients (FXTs) that it is uncovering. These FXTs show a wide range of properties and some have been linked to known transient classes including gamma-ray bursts (GRBs). In this talk, I will discuss one recently detected FXT with unique and fascinating behaviour, EP250108a/SN 2025kg or the ‘kangaroo’. EP250108a is an unusually long FXT and its optical characteristics are similarly atypical with an early fast cooling thermal phase followed by a type Ic broad lined supernova. I will explore how the X-ray, optical and radio data combine to show that this early emission could be one of the first observed examples of a shocked cocoon resulting from a trapped jet. I will also present our analysis of the supernova itself, which closely resembles supernovae linked to GRBs, and discuss the implications for the progenitor system. Finally, I will compare to other fast transients and discuss the broader implications for the wider FXT and GRB populations uncovered by this unique event.

404 Exploring low-luminosity afterglows - automated optical follow-up of Swift GRBs with Palomar-60 inch telescope

The Palomar 60-inch (1.5 metre) telescope conducted an automated optical GRB follow-up programme from 2005 to 2017. It was configured to respond automatically, in less than three minutes, to well-localised GRB alerts, and it was one of the largest optical telescopes with such a programme at the time. The rapid response to the alerts resulted in 88 follow-up observations within one hour of Swift trigger, with a 63% afterglow detection rate and a typical depth of a single exposure of r ~ 20 mag. The resulting sample of 55 afterglows makes the dataset a valuable tool for investigating the entirety of the GRB population. This talk presents the first results from the full 13-year long sample, including an investigation of the decay and spectral properties of P60 afterglows, as well as their luminosity distribution and time-dependent optical luminosity function. The full dataset, combined with observations from other facilities and compared with numerical models of afterglows, will be used to characterize GRB jet properties, such as energy ranges or opening angles, as well as the true rates of relativistic jets. The results provide insight into the population of low-luminosity relativistic transients and their connection to X-ray transients, bridging the gap to a parameter space now explored by Einstein Probe and SVOM.

405 Direct emission and absorption line metallicities of a GRB host at z=4.28 using JWST/NIRSpec

We present the first gamma-ray burst (GRB) host galaxy with a measured absorption line and electron temperature (T$_e$) based metallicity, using the temperature sensitive [OIII]$\lambda$4363 auroral line detected in the JWST/NIRSpec spectrum of the host of GRB 050505 at redshift $z=4.28$. This direct measurement of the emission line metallicity allows us, for the first time, to bridge the gap between the ionised and neutral ISM in a GRB host galaxy at high redshift. We find that the metallicity of the neutral interstellar gas, derived from the absorption lines in the GRB afteglow, is in reasonable agreement with the T$_e$-based emission line metallicity in the ionised gas of the GRB host galaxy. When using strong emission line diagnostics appropriate for high-z galaxies and sensitive to ionisation parameter, we find good agreement between the strong emission line metallicity and the other two methods. Our results imply that, for the host of GRB050505, mixing between the hot and the cold ISM along the line of sight tot the GRB is efficient, and that GRB afterglow absorption lines can be a reliable tracer of the metallicity of the galaxy. This result has important implications for the use of GRB afterglows as probes of the cosmic chemical evolution, although it will have to be confirmed with a larger sample.

406 Unveiling the Secrets of Gamma-Ray Bursts: A Spectro-Polarimetric Journey into Prompt Emission Mechanisms

The radiation mechanism of the prompt emission is still an open issue and can be resolved using a systematic and uniform time-resolved spectro-polarimetric study. In this work, we performed a comprehensive investigation of the spectral, temporal, and polarimetric characteristics of bright GRBs observed using the AstroSat CZTI, Fermi GBM, and Swift-BAT to provide insight into the prompt emission radiation mechanisms. We investigated the time-resolved (in 100-600 keV) and energy-resolved polarization measurements of these GRBs with an improved polarimetric technique. In addition, we also carried out detailed time-resolved spectral analyses of these GRBs using empirical and physical synchrotron models. By these improved time-resolved and energy-resolved spectro-polarimetric studies, we could pin down the elusive prompt emission mechanism of these GRBs. Our spectro-polarimetric analysis reveals that GRB 160821A has a Poynting flux-dominated jet. On the other hand, GRB 160325A and GRB 160802A have a baryonic-dominated jet with mild magnetization. Furthermore, we observe a rapid change in polarization angle by ~ 90 degrees within the main pulse of very bright GRB 160821A.

Additionly, I will also discuss the spectro-polarimetric analysis of the second brightest burst, GRB 230307A, using data from Fermi, Konus-Wind, and AstroSat. In this analysis, we discovered evidence of a transition from a Baryonic to a Poynting flux-dominated jet composition within the burst’s duration. Our study suggests that the jet composition of GRBs may exhibit a wide range of magnetization, which can be revealed by utilizing spectro-polarimetric investigations of the bright GRBs.

407 Extended emission of merger GRBs from high latitude emission and time propagation effects.

Long GRBs are traditionally thought to come from collapsing stars and short GRBs to originate from binary neutron star mergers. However, the discoveries of kilonovae coincident with GRB 211211A and GRB 230307A provide conclusive evidence that some long GRBs can in fact originate from BNS mergers. These long merger GRBs can in part be classified by the existence of an extended plateau of emission after the initial prompt spike in their lightcurves, termed extended emission. The source of this extended emission is still debated. In this talk I will present a shell model that utilises high latitude emission and frame propagation effects to produce extended emission-like lightcurves. Our results show that the timescales of these long mergers can be reproduced through geometrical and frame transformation effects only, without the need for an additional source of energy injection. I will show that our model is capable of producing the broad features of extended emission including spectral evolution such as that seen in GRB 211211A (Gompertz et al, 2022).

408 Probing the axial symmetry of gamma-ray burst jets using afterglow polarimetry

Polarisation measurements of gamma-ray burst afterglows provide a powerful tool for probing the structure of relativistic jets.

In this talk, I will discuss polarisation signatures of gamma-ray burst afterglows, emphasising deviations from the classical model for axisymmetric top-hat jets, which predicts two polarisation peaks and a 90-degree position angle rotation.

Observations of events, such as GRB 170817A have demonstrated that GRB jets can be structured, with the late-time afterglow consistent with a structured jet viewed off-axis.
Structured jets will typically show a single peak in the afterglow along with an unchanging position angle.

Using a toy model we developed; we examine polarisation signals for non-axisymmetric top-hat and structured jets. For non-axisymmetric top-hat jets, the polarisation curve maintains the two-peak structure but no longer drops to zero in-between, and position angle rotations can deviate significantly from 90 degrees. Structured non-axisymmetric jets exhibit a single peak and a gradually evolving position angle.

I will also briefly explore the implications for GRB events with non-standard polarisation angle rotations such as GRB 210610B in which a $54 \pm 9$ degree rotation was observed near a break in the light curve.

Jet asymmetry also leaves a signature on the afterglow light curve; the possibility of constraining the jet’s geometry from multiple breaks observed in the light curve will be discussed.

Illuminating the Faintest Galaxies: Dwarf Galaxies as Probes of Dark Matter, Feedback, and the First Stars

Organisers: Alejandra Aguirre-Santaella, Shaun Brown, Ting-Yun (Sunny) Cheng, Jessica Doppel, Isabel Santos-Santos, Joaquin Sureda

Dwarf galaxies are the most numerous yet faintest type of galaxy in the Universe. As the most dark matter dominated systems in our Universe they offer a powerful laboratory to probe the nature of this elusive form of matter and search for potential decay signals. Their observed abundance and distribution can place strong constraints on different dark matter models.

Dwarf galaxies also serve as powerful tools for exploring the limits of galaxy formation, as they form in the smallest haloes. Their shallow potentials provide an excellent testing ground for feedback processes, such as supernovae, stellar winds, and AGN feedback. At the faintest end of the luminosity function, ultra-faint dwarfs are believed to be relics from the epoch of reionization, providing insights into the physics of reionization, the first stars, and early galaxy formation.

In the local Universe, dwarf galaxies offer the most detailed studies of stellar populations, kinematic analyses, and chemical abundances. These observations are critical benchmarks for validating and refining predictions from cosmological simulations. Upcoming facilities and surveys such as Euclid, LSST, Roman, WEAVE, 4MOST, SDSS-V, SKA, CTA and MeerKAT, will soon provide deeper and higher resolution observations for countless more dwarf galaxies, revolutionising our view of the Universe in the low-mass regime.

This session aims to foster interdisciplinary discussion and collaboration between observers and theorists working on dwarf galaxies from the classical to the ultra-faint regime. As a world leader in dwarf galaxy science the UK is well placed to fully exploit this new wealth of data.

409 LYRA: Intrinsic stellar distributions in the faintest dwarf galaxies

In our understanding of galaxy evolution, dwarf galaxies represent a key ingredient, as these act as the building blocks of larger galaxies, and they can help us understand the early stages of the first galaxies in the Universe. In the context of simulations, the dwarf galaxy mass scale represents a challenge itself just to be able to resolve them within a cosmological box. State-of-the-art zoom-in simulations solve this issue but still rely on the chosen sub-grid physics model to account for the processes involved. For instance, supernova feedback is a fundamental process regulating the evolution of dwarf galaxies and, therefore, sensitive to the chosen model. LYRA is a new set of zoom-in cosmological hydrodynamical simulations designed to resolve the formation and evolution of dwarf galaxies in great detail. These simulations have a baryonic mass resolution of 4 $M_\odot$, hence resolving individual stars above that and supernovae shocks self-consistently, removing the need for sub-grid physics implementation of this process. These simulations offer a promising avenue for advancing our understanding of the formation and assembly of dwarf galaxies, their stellar populations, and the influence of baryon physics in their assembly history. I will present some results from these simulations, focusing on the connection between the stellar distribution and the underlying dark matter halo. I will show how the stellar morphology evolves and how it can provide information on the effects of reionisation and the dark matter halo.

Speaker: Joaquin Sureda (Durham University)

410 Dwarf galaxies in the UNIONS survey

Dwarf galaxies provide critical tests for cosmological models by probing $\Lambda$CDM predictions at sub-galactic scales. Despite their importance, detecting these faint systems beyond the Local Group remains challenging due to their diffuse nature and low surface brightness. In this talk, I will present results from our recent large-scale search for dwarf galaxy candidates in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) - a wide, deep, multi-band survey covering nearly 5,000 square degrees of the northern sky. We developed an automated detection pipeline that first preprocesses multi-band imaging data through binning, artifact removal, and stellar masking before employing the software MTObjects to detect low surface brightness objects. After parameter-based filtering and cross-matching between g, r, and i bands, we fine-tuned the deep learning model Zoobot, originally trained on Galaxy Zoo classifications, to identify dwarf candidates. Our training dataset incorporated visual classifications from multiple experts, capturing both consensus and uncertainty in dwarf identification. Applied to $\sim$1.5 million objects, our method identified over 23,000 dwarf galaxy candidates with probability scores > 0.8, of which $\sim$8,000 have probabilities exceeding 0.9. The spatial distribution of high-confidence candidates reveals a correlation with massive galaxies (log$(M_{*}/M_\odot) \geq$ 10) within 120$\,$Mpc, suggesting many are genuine satellites. Despite the high-confidence classification, these objects remain candidates that would benefit from spectroscopic follow-up to confirm their nature and obtain crucial distance measurements. We present this catalog as a community resource to advance studies of galaxy formation, hierarchical structure assembly, and the distribution of dwarf galaxies across diverse cosmic environments.

Speaker: Nick Heesters (École Polytechnique Fédérale de Lausanne (EPFL))

411 The morphological mix of dwarf galaxies in the nearby Universe using ultra-deep optical imaging in the COSMOS field

The morphological mix of dwarf galaxies (M < 10^9.5 MSun) outside the very local Universe is essentially unknown, due to the past unavailability of surveys that are both wide and deep. Here, we use 257 dwarf galaxies to present the first unbiased, statistical study of dwarf galaxy morphologies at cosmological distances (0.03 < z < 0.1), by combining physical parameters from the COSMOS2020 catalog with deep optical images from the Ultra-Deep layer of the HSC-SSP survey.

We combine quantitative morphological parameters (e.g. CAS, M_20 and Gini) with visual classification of 257 dwarf galaxies to show that dwarfs fall into three general classes: early-types i.e. E and S0 (43%), spirals (45%) and a third class which corresponds to a featureless flat profile with no noticeable spiral or bar features and low central concentration (10%). While the number fraction of early-types and spirals is comparable to that in the massive regime, the featureless galaxies are completely missing in the massive regime. Compared to their massive counterparts, dwarf early-types show a much lower incidence of interactions, are significantly less concentrated and share similar rest-frame colours as dwarf late-types. This suggests that the formation histories of dwarf and massive early-types are different, with dwarf early-types being shaped less by interactions and more by secular processes.

Our study serves as a pilot to what will be possible using the hundreds of thousands of dwarfs that will be imaged by revolutionary deep-wide surveys like the Legacy Survey of Space and Time (LSST).

412 Dwarf Galaxy Growth Across the Cosmic Web

Dwarf galaxies are considered laboratories for studying the assembly of galaxies in the early universe, and their properties at final day may vary as a function of environment. In our work, we used the DM-only simulation COCO, along with the semi-analytic model GALFORM to investigate the differences in dwarf stellar mass assembly between different areas of the cosmic web. Our findings show large trends in the stellar mass assemblies of dwarfs, with satellites in nodes assembling an average of 1.78 Gyrs earlier than satellites in walls, but only 0.23 Gyrs earlier for central galaxies. Satellite galaxies show strong dependence of mass assembly on environment, which is driven predominantly by the epoch at which an object becomes part of a larger host in different regions of the cosmic web. On the other hand, central galaxies do not show trends as significant as those of their host dark matter haloes due to the differences in the stellar to halo mass relation between different areas of the cosmic web. We also investigate the effect of varying parameters controlling the timing and filtering scale for reionisation, finding significant effects particularly in the regime of ultrafaints. This work is unique in providing a statistical investigation of the stellar mass assemblies of galaxies in this mass regime, and how those properties depend on the parameters of reionisation.

413 THE ORIGIN OF THE PLATEAU IN THE STELLAR MASS METALLICITY RELATIONSHIP

The stellar mass-metallicity relation (MZR) is a strong correlation between $M_*$ and [Fe/H], but below $M_* \sim 10^5$\,M$_\odot$, it flattens with increased scatter. This has been linked to a top-heavy initial mass function, tidal stripping, or Population III stars, but no definitive cause is known. We explore whether environmental effects explain this plateau.

We show that tidal stripping moves galaxies leftward in the MZR, inducing scatter, but most Milky Way satellites show little stellar mass loss, making tides an unlikely primary cause. Quenching during early evolution can freeze in metallicity scatter in isolated EDGE dwarfs at $M_* < 10^4$\,M$_\odot$. This owes to scatter in their central densities, which affects star formation and metal enrichment rates, and in the accretion of low-metallicity gas (`dilution’). However, it fails to explain the highest metallicities observed ([Fe/H] $\sim -2$).

Instead, "dwarfs-of-dwarfs" in EDGE simulations naturally populate the plateau at $M_* < 10^4$, with scatter comparable to real data, sometimes reaching [Fe/H] $\sim -1$. This results from two effects: pollution of metal-rich gas from a nearby host dwarf and confinement of outflows by the circumgalactic medium. Since these effects occur in satellite dwarfs long before they encounter a larger galaxy like the Milky Way, we predict that the plateau and its scatter should be present in most environments, except in extreme isolation.

414 Distribution Functions of Low-Mass Star-Forming Galaxies

Detecting and characterizing the low-mass galaxy population is one of the frontiers of astrophysics research. Observational measurements of such small ('dwarf') galaxies are particularly challenging due to their low surface-brightness. Therefore, the galaxy stellar mass function (GSMF), which helps us probe the halo mass function (HMF) and the underlying cosmology, suffers from uncertainties in low-mass regime. As low-mass star-forming galaxies are more likely to be centrals, these systems are key for measuring the GSMF and HMF in this mass regime. Moreover, for this type of galaxies, the star-formation rate density (SFRD) as a function of stellar mass provides a straightforward relation to the GSMF and allows us to characterize this population more thoroughly in a cosmological volume as galaxies with higher star-formation rates are easier to detect. In this work, we use two suites of high resolution cosmological simulations, EAGLE and TNG50, to perform a detailed study of their low-mass star-forming galaxy populations and of the relation of SFRD as a function of stellar mass, SFRD(M$_{*}$). We investigate this relation at different redshifts and use it as a new "metric" to make comparisons between the two sets of simulations, and with the observational measurements from the GAMA, MUSE and SDSS surveys. Our results indicate that the SFRD has a constant slope down to stellar masses of $10^{5.5} M_\odot\ $ and therefore there does not appear to be a turn-over in the GSMF at the low-mass end. The slope exhibits variations on different mass ranges and also with different physics prescriptions.

Speaker: Sakircan Beyazit (Liverpool John Moores University)

17:39 Poster Flash Presentations

Magnetic reconnection, topology and non-ideal instabilities

Organisers: Alexander Russell, Jonathan Eastwood, Gunnar Hornig, James McLaughlin, Christopher Prior, Julia Stawarz, Peter Wyper, Anthony Yeates

Magnetic reconnection is one of the most important processes in solar, space and astrophysical plasmas. In a highly conducting plasma with large length scales, magnetic field connections between plasma elements are conserved, allowing the accumulation of magnetic energy over time. However, conservation of connectivity can break down in small volumes – this has global consequences, for example enabling rapid conversion of magnetic energy in solar flares, auroral substorms and astrophysical jets and disks.

This session aims to bring together researchers working on magnetic reconnection, magnetic topology and resistive and collisionless instabilities, from the solar, space and astrophysics communities. Cross-cutting scientific discussions will cover theory, simulations, remote observations and in-situ observations.

Some of the key questions we are interested in addressing are:
o What do the latest numerical simulations and observations reveal about reconnection and non-ideal instabilities?
o How do recent new perspectives on topological properties, such as magnetic skeletons or helicity, shed light on dynamics such as flaring and coronal heating?
o How does turbulence affect reconnection, and vice-versa?
o How have results from the latest missions (e.g. Solar Orbiter and MMS), observatories (e.g. DKIST) and analysis tools (e.g. field line helicity) changed our understanding of these topics?

415 Theory and observation of plasmoid-modulated magnetic reconnection

The short timescale of the solar flare reconnection process has long proved to be a puzzle. Studies suggest the importance of the formation of plasmoids in the reconnecting current sheet, with quantifying the aspect ratio of the width to length of the current sheet in terms of a negative power $\alpha$ of the Lundquist number, that is, S$^{-\alpha}$, being key to understanding the onset of plasmoids formation. In this talk, we present our application (the first of its kind) of theoretical scalings for this aspect ratio to observed flares. By doing this we are able to evaluate how plasmoid formation may connect with observations. For three different flares that show plasmoids we find a range of values of $\alpha$=0.26 to 0.31. This is close to the theoretically predicted value, but due to the presence of α in the exponent of the power-law, these differences are somewhat difficult to reconcile. The values in this small range implies that plasmoids may be forming before the theoretically predicted critical aspect ratio ($\alpha=1/3$) has been reached, potentially presenting a challenge for the theoretical models. We will discuss the implications for understanding flare reconnection and how to potentially reconcile these differences.

416 The Thermodynamics of Naturally Heated Coronal Null Points

Magnetic null points are regions within a magnetic field where the field strength vanishes and are commonly associated with various forms of heating. A previous study of ours showed that there are interesting restrictions on the flow of heat at null points due to their magnetic geometry. This causes null points to take on strikingly different thermal structures that depend on the form of artificial heating. In this presentation we investigate the thermal structure that arises in a simple magnetic geometry, containing a null, that is energised in a natural way, by magnetic reconnection. We find that the typical structure that arises is in excellent agreement with our previous (much simpler) work and we discuss the implications of this result.

417 Oscillatory Reconnection: A Comparison with Steady-State Solutions

Magnetic reconnection is a fundamental plasma process at the heart of many dynamic events such as solar flares. Despite reconnection events being dynamic, models of reconnection are often based off steady state solutions such as Sweet-Parker reconnection and Pestchek reconnection. In this study we investigate oscillatory reconnection, a time-dependent form of reconnection, and how it compares to those steady state models. The ShockID algorithm (Snow et al 2021) is used to identify the MHD shocks within the oscillatory reconnection mechanism, resulting in the identification of Petschek-like slow mode shocks at the edges of the current sheets as well as fast-mode termination shocks and slow-mode deflection shocks in the reconnection outflows. An investigation into the energetics of the system is also carried out, focusing on the conversion of energies and the proportion of the total energy conversion within the system that is due to the shocks that are present. Finally, diamond like structures in the reconnection exhausts are reported on for the first time including their similarities with Mach Diamonds found in supersonic gas jets.

418 Automatic Detection of Fine Structures in Solar Flare Ribbons

Solar flares are explosive events in which magnetic reconnection rapidly converts stored magnetic energy into bulk motion, plasma heating, and particle acceleration. Observations of solar flare ribbons reveal various fine structures, including wave-like perturbations and spirals, which theory suggests are linked to plasmoids formed via tearing-mode instabilities in the flare current sheet. Because these substructures capture key information about turbulent magnetic reconnection, studying them closely can yield vital insights into how the flare current sheet fragments.
In this work, we leverage the self-similar nature of these fine structures to develop an automatic detection method for identifying them in our high-resolution 3D MHD simulations. This method assists us in tracing the plasmoids throughout the flare event, offering a more detailed picture of the underlying reconnection dynamics. Inferring the dynamics of the flare magnetic reconnection is an important step toward advancing our understanding of space weather.

419 Investigating the Effects of Atmospheric Stratification on Coronal Active Region Field Modelling

Understanding the evolution of the complex magnetic fields found in solar active regions is an active area of research. There are numerous models for such fields which range in their complexity due to the number of known physical effects included in them, the one common factor being they all extrapolate the magnetic field up from the photosphere. In this study we focus on the fact that above the photosphere and below the corona lies the relatively cool and dense chromosphere -- which is often neglected in coronal models due to it being comparatively thin and difficult to model. We describe a series of 2.5D and 3D simulations using both MHD and magnetofriction which seek to isolate these effects, including a new method for automated boundary driving using SHARP magnetogram data. We find that including a cool and dense stratified layer can result in significant changes to the dynamics of an erupting field far higher in the atmosphere than the chromosphere itself, generally delaying eruptions and resulting in flux rope equilibrium positions much lower in the corona than if it is neglected. In the analysis of these fields we make extensive use of topological quantities such as the winding and field line helicity to investigate the complex structures that form as a result.

The Extremely Large Telescope: Science and Instrumentation

Organisers: Kathryn Hartley, Aurelie Magniez, Deborah Malone, Kieran O'Brien

The European Extremely Large Telescope (ELT) is currently under construction by a consortium of leading research institutes across Europe, including notable contributions from institutions in the UK. This groundbreaking telescope is poised to usher in a new era of high-resolution imaging, facilitated by its advanced adaptive optics systems and highly sensitive instruments.

This session will offer a platform for project participants to showcase their contributions to the construction of the telescope and its scientific instruments. Additionally, it will provide an overview of the anticipated scientific missions and the transformative impact these missions are expected to have on our understanding of the universe. Attendees will gain insights into the innovative technologies employed, the collaborative efforts driving the project, and the future research opportunities enabled by the ELT.

Timetable_#67.csv

16:15 Prep time

420 The Evolution of MOSAIC

I will describe the process of evolution of the ELT MOSAIC instrument from its original Phase A concept to the final architecture now in detailed design. Substantial changes in the design arose from hard questioning of initial assumptions and have substantially improved the feasibility and performance of the instrument.

Speaker: Gavin Dalton (University of Oxford/RALSpace)

421 ANDES: From Exoplanets to Fundamental Physics with High Resolution Spectroscopy

The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is a powerful high-resolution spectroscopy instrument for the ELT that will operate over a minimum simultaneous waveband of 0.4-1.8µm, with the goal of being extended to 0.35-2.4µm with a K-band spectrograph. Consisting of fibre-fed spectrographs – UBV, RIZ and YJH – and providing a spectral resolution of ~100,000, ANDES will offer insight into a broad range of science cases.

Amongst these are the characterisation of exoplanet atmospheres and protoplanetary disks, along with their stellar hosts, through transit spectroscopy. ANDES aims to be the first instrument to unambiguously determine fingerprints of population III stars. It will be used to directly measure cosmic expansion and test for potential variations in fundamental constants. To achieve these objectives, ANDES must meet the required wavelength calibration stability of 1 m/s over 24 hours, with a goal of 0.02 m/s over 10 years, in addition to requirements on spectral resolution and wavelength range.

This talk will provide an overview of the ANDES instrument and its science objectives, with a focus on the UK’s contribution. Alongside Canadian partners, the UK will deliver the YJH spectrograph – likely to be the largest cryogenic, ultra-stable, high-resolution spectrograph ever built. Through the use of dual slits, this spectrograph will have the unique ability to operate in both seeing and diffraction-limited observing modes interchangeably. We will also present the baseline spectrograph design, which relies on the technology development of an echelle grating mosaic, over a metre in length, to accommodate the large beam size.

Speaker: Vinooja Thurairethinam (UK Astronomy Technology Centre)

422 On-sky validation of SPRINT: the ELT approach for tracking alignment within adaptive optics systems

The size and complexity of modern ground-based telescopes, such as the Extremely Large Telescope (ELT), present new challenges for adaptive optics (AO) systems. Large separations between the deformable mirror (DM) and the wavefront sensor (WFS), with moving components in the optical path, mean the alignment between them is expected to regularly evolve during observations. Without tracking and correction, these mis-registrations between the DM and WFS degrade the AO performance. Accounting for these effects at the ELT is crucial for achieving diffraction limited performance and realising the full resolution potential of the telescope. SPRINT (System Parameters Recurrent INvasive Tracking) provides an approach to track these mis-registrations and is planned to be used by all ELT instruments. It uses a pseudo-synthetic model of the AO system to estimate the mis-registrations from on-sky signals. We present an overview of SPRINT, and the results from testing at the Large Binocular Telescope to validate the method. These first daytime and on-sky tests demonstrate the robustness and accuracy of SPRINT.

Speaker: Ben Buky (STFC - UK Astronomy Technology Centre)

423 Stars lensed by the supermassive black hole in the centre of the Milky Way: predictions for future telescopes

Gravitational lensing is an important prediction of general relativity, providing both its test and a tool to detect faint but amplified sources and to measure masses of lenses. For some applications (e.g., testing the theory), a point-like source lensed by a point-like lens would be more advantageous. However, until now only one gravitationally lensed star has been resolved. Future telescopes will resolve very small lensing signatures for stars orbiting the supermassive black hole (SMBH) in the centre of the Milky Way. The lensing signatures, however, should be easier to detect for background stars. I will show the prediction that the Extremely Large Telescope (ELT), Thirty Meter Telescope (TMT), and Giant Magellan Telescope (GMT) will resolve the lensed images of around 100 stars in the background of the SMBH in the centre of the Milky Way. I will also describe what observational characteristics are needed to achieve this (resolution and depth). Finally, I will discuss other observational signatures of lensed stars, which could be searched for with high-resolution infrared instruments.

Speaker: Michał Michałowski (Adam Mickiewicz University in Poznan)

424 Observing with MOSAIC and its wide-field AO system

MOSAIC is the only instrument proposed for the Extremely Large Telescope (ELT) that makes use of the full 10 arc minute field of view of the telescope.. The Ground Layer Adaptive Optics (GLAO) system for MOSAIC does not reach the diffraction limit but is designed to provide partial AO correction over this entire field, providing up to 1.5x the flux within a MOS aperture over that obtained with the telescope-delivered image quality. To achieve this, the GLAO system uses wavefront information from multiple laser and natural guide stars to identify only turbulence closest to the ground which is common to all lines of sight. Determining performance in this mode and understanding the interaction with the telescope control system is challenging, and places constraints both on system performance and the way in which astronomical observations can be made with MOSAIC. Here we describe some how the design and operation of the MOSAIC instrument addresses these challenges and how the AO system design has been optimised to enable wide-field multi-object spectroscopy.

Speaker: Tim Morris (Durham University)

Planetary science and exploration

Organiser: UK Planetary Forum (UKPF); co organisers: Peter Fawdon, Mark Fox-Powell, Dimitri Veras, Duncan Lyster, James Darling, Jordan Stone, Karen Devoil, Lee White, Martin Subtle, Megan Schwamb, Peter Mc Ardle, Stephanie Halwa, Tom Harvey, Mark Nottingham

The UK is home to an internationally significant research community devoted to the study of the formation and evolution of planetary bodies in our Solar System and beyond. This session aims to (1) showcase the latest research from across the breadth of UK planetary science, and (2) identify areas of mutual scientific interest and catalyse collaboration across geoscience, planetary science, and astronomy. Topics include (but are not limited to): Analysis and experimental investigations of planetary materials; (e.g., meteorites, lunar, martian and terrestrial samples); Remote sensing and modelling of planetary bodies; (e.g., geology and surface processes of terrestrial planets, icy moons and small bodies, observations and models of planetary atmospheres and giant planets); Ongoing and upcoming exploration of planetary bodies in our Solar System (e.g., Mars rover missions, lunar exploration, BepiColumbo, JUICE, Europa Clipper). Additionally, we welcome submissions concerning the ethics and astrobiological considerations of Solar System exploration.

16:15 Prep time

425 Energetic Electron Observations During BepiColombo’s Mercury Flybys

Mercury hosts a dynamic and highly variable magnetosphere shaped by its weak intrinsic magnetic field and the intense pressure of the solar wind. Previous observations from spacecraft sent to the planet have provided key insights into Mercury’s magnetospheric structure and energetic particle populations, revealing transient and highly variable energetic electron enhancements within the planet’s magnetosphere. We present BepiColombo/SIXS observations of energetic electron populations in Mercury’s magnetosphere during the spacecraft’s flybys of the planet. Although no such populations were observed during the first flyby, strong energetic electron signatures were observed during the second and third flyby. These observations are further discussed in the context of observations by MESSENGER (Lawrence et al., 2015) in the invariant latitude-MLT plane, showing good agreement between the two data sets.

Speaker: Dr Liam Edwards (University of Helsinki)

426 Detecting and Measuring Transverse Aeolian Ridges (TARs) on Mars using Deep Learning.

In this investigation a deep learning (DL) neural network was used to detect Transverse Aeolian Ridges (TARs) in High Resolution Imaging Science Experiment (HiRISE) images of the surface of Mars. TARs are decametre scale bedforms which are found ubiquitously on the surface of Mars. They consist of ridges aligned perpendicular to the direction of the prevailing peak wind. Because these features are mostly immobile in the present day they have significance as a geomorphic marker of past wind conditions.
In order to derive statistically significant data related to TAR morphometry, distribution, and orientation, it is necessary to segment them in large numbers. A HiRISE image where TARs are present will likely have 1000s to 10,000s of features. This makes manually segmentation challenging.
We developed a semi supervised pipeline for automatic retrieval of TAR features within a Geographic Information System (GIS) environment. A Mask R-CNN model segments candidate TARs. These are stored as a polygon feature class which is fed into a series of GIS tools which clean up the dataset, for example by filtering out features which are likely to be false positives based on morphometry characteristics not expected for TARs. Morphometry and orientation statistics are then computed.
The model was trained using a desktop workstation computer, using commercial off the shelf models. This demonstrates that machine learning is becoming increasingly accessible and will likely see increasing use in the field of Earth and Planetary Science.

16:48 Poster Flash Presentations

427 Characterisation of planetesimals using white dwarfs

White dwarfs can be used as tools to measure the composition of exo-planetesimals. Any metals observed in their otherwise pure hydrogen/helium atmospheres must be from accretion of planetary objects. Spectroscopic observations of these white dwarfs allow us to measure their atmospheric abundances, and thus the abundances of the accreted material.

This method has been applied to hundreds of white dwarfs, revealing a great diversity in planetary compositions, including differentiated bodies, primitive material, comets, and ice giants. Many studies have made use of the work performed by the Solar System planetary body field. Extensive and detailed studies have measured the composition of many small Solar System bodies, which we use to characterise the type of material accreted by white dwarfs.

In my talk, I will discuss my work regarding three white dwarfs accreting i) the most core-rich exo-planetesimal discovered, ii) a primitive chondritic body with a silicon depletion, and iii) a volatile-rich Kuiper Belt-like object. I will show how Solar System studies were used to interpret the nature of this material. I will also demonstrate how white dwarf planetary science can be used to further aid the Solar System planetary body field.

Closer collaboration between these two fields will be of great mutual benefit.

428 The Fluvial History of Noachis Terra, Mars

The nature of the Martian climate during the Noachian-Hesperian transition (~3.7 Ga), and how surface features such as Valley Networks (VNs) and lakes associated with liquid water formed, is debated. There are two end-member theories. The first is that warm and wet conditions persisted on early Mars long enough that liquid water was stable on the surface for extended periods. The second is that Mars was generally cold and dry, and that geological features indicative of flowing water (e.g. VNs) were formed only very sporadically by meltwater from ice sheets during short climate excursions.
Noachis Terra, in Mars’ southern highlands, is a region where ‘warm, wet’ climate models predict high rates of precipitation, but is poorly incised by VNs. We searched instead for Fluvial Sinuous Ridges (FSRs, aka inverted channels) here as they provide alternate evidence to VNs for stable surface water. We used CTX, MOLA, and HiRISE data and recorded location, length and morphological characteristics.
We find FSRs to be common across Noachis Terra, with a cumulative length of more than 15,000 km. These are often isolated segments, but some systems are hundreds of km in length.
The broad distribution of FSRs suggests a broadly distributed source of water. The most likely candidate is precipitation, suggesting a benign surface environment. For FSRs to have formed mature, interconnected systems, up to tens of metres high, these conditions must also have been relatively long-lived. This suggests that ~3.7 Ga, Noachis Terra experienced warm and wet conditions for a geologically relevant period.

429 JCMT-Venus: Tracking Key Atmospheric Species in Venus’ Mesosphere

To follow up on the detection of PH₃ in Venus’ clouds (Greaves et al., 2021), we conducted the JCMT-Venus Project, consisting of three multi-week, disc-integrated observing campaigns carried out in February 2022, July 2023, and September 2023. These campaigns aimed not only to reconfirm the presence of PH₃ but also to investigate the broader chemical environment within and above Venus’ clouds. Utilising a ~2 GHz-wide bandwidth, we successfully observed several key species central to Venusian atmospheric chemistry, notably H₂O (via HDO) and SO₂. Our continuous monitoring over multiple weeks enabled an unprecedented analysis of both short-term (day-to-day) and longer-term variations in these key molecules.
Here, we present initial results on the variability of H₂O and SO₂ abundances and establish upper limits for additional candidate gases, such as H₂SO₄ and HCO⁺. These results provide essential context for upcoming missions such as DAVINCI, EnVision, and the MIT-led Morning Star Missions, which will explore the potential habitability of Venus’ clouds.

18:00 3-min to inspire: competition

Learn about the incredible research being done by young people around the country as they explain their thesis IN JUST 3 MINUTES!

Public Talk (open also to participants)

430 The Supermassive Podcast live – black hole special

Join hosts Dr Becky Smethurst, Izzie Clarke and resident astronomer Dr Robert Massey for a live recording of the UK’s most popular astronomy podcast. From bending time to spaghettification, this is your chance to join an audience of some 90,000 space fans around the world and ask the team your burning questions about black holes.

Speakers: Rebecca Smethurst (University of Oxford), Izzie Clarke, Robert Massey (Royal Astronomical Society / University of Sussex)

19:30 Social Event: Quiz

Friday 11 July

08:00 Registration and set up

Galaxy formation simulations at the Frontier

Organisers: Sarah Johnston, Stephen Wilkins; co organisers: Sownak Bose, Sophie Koudmani, Andrew Pontzen, Sandro Tachella

For over a decade, cosmological galaxy formation simulations have had a transformative impact on modern extragalactic astronomy, becoming indispensable tools for understanding galaxy formation and evolution. This session examines three major frontiers in galaxy formation modelling:

Observational Frontier: revolutionary data from the James Webb Space Telescope has revealed unexpected phenomena – surprisingly abundant bright ultra-high redshift galaxies, early SMBHs, and early quiescent galaxies, and unique chemical signatures – posing challenges to current models. Observations from Webb will soon be complemented by upcoming wide-area surveys (Rubin/LSST, DESI, 4MOST, Euclid), and future observatories (SKA, ELTs, LISA) will expand the scope of observational constraints with unprecedented area, sensitivity, wavelength coverage, and resolution. Together these will provide new opportunities to test and refine models.

Meeting these observational challenges is the Physics Frontier: models are continuing to increase in complexity, adding processes like radiative transfer, magnetohydrodynamics, and more sophisticated modelling of SMBHs and star formation.

Meeting the challenge of more sophisticated models and large volumes is the Scale Frontier: thanks to improvements in code efficiency and access to new facilities, entering the exascale regime, simulations can increase in complexity, resolution, volume, or number; with large ensembles of simulations now allowing the systematic exploration of model parameters.

This session will focus on results from these three frontiers: the observations that are challenging current models and informing next generation models, the new physics being implemented, and the prospects for the future in the exascale regime.

431 Exploring the non-equilibrium interstellar medium of population III galaxies in MEGATRON

Since the launch of JWST, the advent of high-redshift spectroscopy has supercharged the discovery of strange objects with anomalous UV brightnesses, unexpected carbon and nitrogen abundance patterns, and ionizing spectra from extremely hot stellar populations, all wrapped up in physical sizes which point to incredible stellar and gas densities. With modern galaxy evolution simulations striving to explore this frontier, it is becoming abundantly clear that doing so accurately requires precise considerations of the formation, evolution and feedback (both mechanical and radiative) from a variety of typical and extreme stellar populations. However, all of this must be done in the context of a well-resolved, multi-phase interstellar medium (ISM) surrounded by the turbulent environment of a high-redshift halo. To this end, I will present first results from the MEGATRON suite of high-resolution cosmological radiation hydrodynamical zoom simulations which for the first time feature non-equilibrium chemistry and heating/cooling processes coupled to on-the-fly radiative transfer: tracing the births and deaths of population III and II stars in the early universe.

Specifically, I will be discussing how the ISM phase structures of high-redshift galaxies evolve as they transition from the population III to population II regime. Furthermore, I will explore the impact that this evolution has on the direct observable properties of these objects, such as their line strengths, UV diagnostic diagrams, UV continuum slopes, and ionizing efficiencies. All of this will be contextualized with present-day JWST observational data, focusing on the few population III candidates that have already been presented in the literature.

432 Burst, quench, repeat: unveiling the evolution of high-redshift galaxies with the THESAN-ZOOM simulations

Recent JWST observations have revealed remarkably compact morphologies, highly bursty star-formation histories, and puzzling chemical abundances in the earliest galaxies. Due to the unprecedented sensitivity and complexity of these datasets, state-of-the-art cosmological simulations are essential for their accurate interpretation. The THESAN-ZOOM simulations, which integrate high-resolution galaxy formation physics with comprehensive, on-the-fly radiative transfer and a detailed interstellar medium model, provide a powerful laboratory for exploring galaxy evolution from redshifts z = 3 to z = 12. In this talk, I demonstrate that star formation becomes increasingly bursty at higher redshifts, driven primarily by stochastic, rapid gas inflows from the intergalactic medium and frequent galaxy mergers. These intense star formation bursts dramatically influence chemical enrichment, producing extreme and unusual chemical signatures such as pronounced nitrogen enhancement and causing an inversion of the fundamental metallicity relation at early epochs. Furthermore, bursty star formation is closely tied to the morphological evolution of galaxies, inducing repeated cycles of central compaction and subsequent expansion via inside-out quenching. By employing sophisticated forward modeling to produce mock JWST observations, we accurately reproduce the extended Hα emission observed at high redshift. Contrary to interpretations that attribute these extended sizes to gradual inside-out galaxy growth, our analysis reveals that extended Hα regions primarily arise from extreme Lyman continuum photon leakage driven by intense central starbursts. Ultimately, this work underscores the indispensable role of cutting-edge simulations in decoding the complex and often counterintuitive physics shaping early galaxy formation, providing critical insights to inform future observational strategies and theoretical developments.

433 The First Light And Reionisation Epoch Simulations: high redshift galaxy evolution in the large volume, high fidelity regime

I will present the First Light And Reionisation Epoch Simulations (FLARES), a series of cosmological zoom hydrodynamic simulations of the epoch of reionisation and beyond. FLARES has become one of the key theoretical comparison suites for the latest results from the James Webb Space Telescope, helping to explain some of the rarest, most extreme galaxies and environments given its unique simulation approach. I will present an overview of some of the key results from FLARES over the past 4 years, including forward modelled line emission, resolved UV to IR maps, size evolution, as well as predictions for evolved, passive populations up to z ~ 7. Finally, I will provide a look to the future of the FLARES collaboration, with particular focus on predictions for wide field surveys, such as Euclid.

434 Cosmological hydrodynamical simulations with variable initial mass functions

Recent JWST observations of high-redshift galaxies, as well as spectroscopic and dynamical studies of nearby early-type galaxies, signal deviations of the stellar initial mass function (IMF) from the form inferred in the Solar neighbourhood. We present results from COLIBRE simulations run with a version of the code adapted to allow the formation of stellar populations with a non-universal IMF, in which metal yields and the energetics of supernova feedback are self-consistently adjusted. Here we choose to make the IMF increasingly top heavy (i.e. weighted more towards massive stars) for stellar populations that form from natal gas of high mass density. The model we have applied yields an elevated far-UV luminosity in young stellar populations without significantly impacting the star formation rate, resulting in high redshift (z > 10) UV luminosity functions that are in strong agreement with recent data from JWST.

435 Testing galaxy formation models with the stellar mass-halo mass relations for star-forming and quiescent galaxies

The tight relationship between the stellar mass and halo mass of galaxies is one of the most fundamental scaling relations in galaxy formation and evolution. It has become a critical constraint for galaxy formation models. Over the past decade, growing evidence has convincingly shown that the stellar mass-halo mass relations (SHMRs) for star-forming and quiescent central galaxies differ significantly: at a given stellar mass, the average host halo mass of quiescent centrals is more massive than that of the star-forming centrals. Despite the importance of this feature, its scientific implications have not yet been fully recognized or thoroughly explored in the field. In this work, we demonstrate that the semi-analytical model L-GALAXIES successfully reproduces these observational results, whereas three state-of-the-art hydrodynamic galaxy formation simulations (TNG, Illustris, and EAGLE) do not. Consequently, in L-GALAXIES, star-forming central galaxies are more efficient at converting baryons into stars than quiescent central galaxies at a given halo mass, while the other models predict similar efficiencies for both populations. Further analysis reveals that these fundamental discrepancies stem from distinct evolutionary paths on the stellar mass-halo mass plane. We show that the observed SHMRs for star-forming and quiescent galaxies support galaxy formation models in which quenching only weakly correlates with halo assembly histories, and in which the stellar mass of star-forming galaxies can increase significantly since cosmic noon. In contrast, models in which quenching strongly prefers to happen in early-formed halos are not very favored.

Speaker: Kai Wang (Durham University)

436 The contribution of "orphan" galaxies to the ultrafaint population of MW satellites

The last decade has seen a rise in the number of known Milky Way (MW) satellites, primarily thanks to the discovery of ultrafaint systems at close distances. These findings suggest a higher abundance of satellites within $\sim30$kpc than predicted by cosmological simulations of MW-like halos in the CDM framework. If taken at face value, this discrepancy implies that halos as small as V$_{\rm peak}\sim10$ km/s should host galaxies, challenging CDM and conventional galaxy formation models based on atomic hydrogen cooling.

However, recent studies have highlighted that numerical simulations suffer from artificial subhalo disruption, leading to the premature loss of galaxies due to tidal stripping (so-called “orphan” galaxies).

We use the Aquarius MW-halo simulations combined with the GALFORM semi-analytic galaxy formation model to track orphan galaxies and estimate the true abundance and radial distribution of MW satellites expected in LCDM.
We estimate present-day luminosities and sizes by applying a stellar stripping model based on CDM “tidal tracks”. Strikingly, orphans make up half of all satellites in our highest-resolution run (m$_{p}\sim10^3$M$_\odot$), primarily occupying the central regions of the MW halo. We predict that dozens of satellites should be observable within ~30 kpc of the MW, awaiting discovery through deep-imaging surveys like LSST.

Our unprecedented results resolve any tension with current observations, and evidence the crucial need for "orphan" modelling in studies of the MW's ultrafaint regime. The use of semi-analytic galaxy formation models will be indispensable for the next generation of ultra-high-resolution MW simulations, where hydrodynamical counterparts will remain unfeasible.

Ins and Outs of Accretion: The Consequences of Mass Transfer onto Compact Objects

Organisers: Noel Castro Segura, Melissa Ewing, Scott Hagen, Amy Knight, Martina Veresvarska, Federico Vincentelli

Accretion processes are ubiquitous throughout the universe and play a crucial role in the evolution of astrophysical systems across all size scales. Accretion often occurs in binary systems like white dwarfs and X-ray binaries, which can host neutron stars or stellar mass black holes. Here, the gravitational pull of a compact object draws material from its companion star, resulting in bright emission across the electromagnetic spectrum. The consequences of accretion in binaries are widespread and vital when investigating supernovae progenitors, energetic transients and gravitational regimes. Despite the diversity among accreting systems, accretion itself is scale-invariant. Therefore, gathering the accretion community at NAM is essential to foster discussions of the connections and analogies between different classes of accreting systems and the advancements from forthcoming missions like NewAthena.

In this session, we will discuss the inward and outward flow of mass, energy and angular momentum in white dwarf, neutron star and black hole binaries and their consequences, covering topics from accretion disc radiation and outflows to thermonuclear bursts and quasi-periodic oscillations. Historically, high-energy astrophysics sessions at NAM have combined discussions of accreting binaries with supermassive black holes.

09:00 Prep time

437 The accretion-outflow connection in accreting binaries: 5 key physics challenges

Disc winds are ubiquitous in accreting binaries and have an intimate connection to the accretion disc; however, the driving mechanism of the winds and their impact on the observed spectrum remain poorly understood. In this talk, I will first review the physics behind accretion disc winds and their observational signatures. I will then discuss how numerical simulations (specifically, hydrodynamics and radiative transfer) can be used to better understand the underlying processes of accretion and outflow driving. I will finish by conducting a brief summary of what I see as 5 key challenges we must address if we are to build a better understanding of the disc-wind connection in accreting compact binaries and other accreting sources such as Active Galactic Nuclei.

438 State-of-the-Art Simulations of Line-Driven Accretion Disk Winds

Disk winds are prevalent in a variety of accreting systems, such as young stellar objects, accreting white dwarfs (AWDs), X-ray binaries, and active galactic nuclei (AGN). In the context of AWDs and AGN, radiation pressure acting on spectral lines has been proposed as a key mechanism for driving these outflows. Although previous hydrodynamical simulations have largely supported this idea, they relied on highly approximate, quasi-1D treatments of ionization and radiative transfer. Here, we present state-of-the-art numerical simulations based on realistic radiation-hydrodynamical (RHD) calculations of line-driven disk winds. Our 2.5D RHD code includes a detailed treatment of frequency-dependent radiative transfer through the wind, the corresponding ionization state, and the resulting radiative accelerations. Applying this method to AWDs, we find that it is far more difficult to power the outflows observed in these systems via line driving than previously thought. Physically, this occurs because the winds are far more prone to over-ionization than suggested by quasi-1D treatments. The same issue also appears to affect AGN, where even moderate X-ray fluxes can overionize the outflow. While these findings challenge the viability of line-driven winds under standard assumptions, observations demonstrate that real disk winds do avoid overionization. This discrepancy reveals a critical gap in our physical understanding of line-driven disk winds. The missing key ingredient(s) may include wind clumping, magnetic fields, or non-standard spectral energy distributions.

439 Optical Outbursts in Intermediate Polars

Cataclysmic variables (CVs) can exhibit rapid increases in optical flux. These bursts are broadly classified into categories based on properties such as total energy, peak luminosity and duration. A subset of CVs, referred to as Intermediate Polars (IPs) possess strong magnetic fields that can disrupt the inner disk regions, and which are thought to rarely exhibit bursts. Previous studies developed diagnostic diagrams to differentiate between burst types (dwarf nova, stellar flares, magnetic gating and/or micronovae), but due to the limited population conclusions remain tentative. We combine TESS and ASAS-SN data to systematically search for and attempt to classify bursts in the known population of IPs, and find that a significantly higher proportion than expected (~40%) of known IPs exhibit optical bursts. We further identify 12 new micronova candidates, nearly doubling the known sample and providing valuable systems to investigate the origin of this phenomenon. We conclude by simulating micronova detection rates in ongoing and upcoming synoptic sky surveys, demonstrating the efficiency of detecting micronova and consolidating our detection rates from archival searches.

440 Upper Limits on Radio Emissions from AM CVn-type Stars

Fundamental questions remain about the accretion and outflow physics of cataclysmic variable stars, and their counterparts, AM CVn systems. In an AM CVn system, both the accretor and donor are white dwarf stars. To date, only one AM CVn system has been detected in the radio spectrum and the mechanism for this is yet to be determined. Using observations from the Karl J. Jansky Very Large Array (VLA), I have obtained the deepest radio constraints to date, for two AM CVn systems: AM CVn and HP Lib. I have cross-matched these data and catalogue data, with large scale surveys such as LOFAR, RACS and VLASS to constrain the population of AM CVns, and investigate the radio emission mechanisms in accreting white dwarf binaries. Additionally, this study aims to contribute to ongoing efforts in understanding whether the radio emissions observed in CVs are due to flares in the atmosphere of the donor star, versus transient jets originating from the accretion disk. In this talk, I will discuss how understanding outflows and radio emissions from accreting white dwarfs such as these may help constrain radio emission mechanisms in CVs and similar compact binaries undergoing accretion.

Speaker: Anwesha Sahu (University of Warwick)

441 Cataclysmic variables that splutter

Cataclysmic Variables (CVs) are close binaries in which a white dwarf is accreting from a donor star that fills its Roche lobe. Whilst the evolution of CVs is an important subject they are also the natural laboratory for studying accretion in other less accessible objects.
The number of confirmed CVs continues to grow thanks particularly to large-scale photometric, spectroscopic and x-ray surveys projects such as ZTF, SDSS,DESI and eRosita.
Whilst analysing over 1700 CV spectra from SDSS and DESI a small proportion ($<1\%$) were found that exhibited peculiar short-term variations in luminosity and by inference accretion. The spectroscopy suggests that these systems are at most weakly magnetic and that they have low accretion rates as both the white dwarf and donor are visible, hence a dwarf nova-like behaviour with recurrent thermal disc instabilities is expected. However the light curves display erratic long-term variability with the systems meandering between a faint and a bright state, similar to the light curves of strongly magnetic CVs (polars). The cause of these long-term variations is currently not understood, and it is not clear how these systems fit into the overall evolutionary model.

Speaker: Keith Inight (University of Warwick)

442 Search of sub-stellar companions of White Dwarfs with X-ray observations

Hard X-ray emission from white dwarfs (WD) is generated by the presence of a stellar companion either by their coronal emission or by an accretion disk formed by the material stripped from the companion. Recent studies have proven that Jupiter-like planets can be the donors of material to create an accretion disk and generate hard X-ray emission. Under this light, here we discuss our X-ray XMM-Newton observations of the accreting WD G29-38 and the Central Star of the Helix Nebula. In addition, we present radiation-hydrodynamic simulations produced with the GUACHO code to study the WD+planet scenario. Synthetic X-ray observations are produced with the help of the CHIANTI database and are compared directly with observations.

443 Accretion Disk Dynamics and Mode Switching in the Transitional Millisecond Pulsar J1023+0038

Transitional millisecond pulsars (tMSPs) are a unique class of neutron star binaries that switch between an accretion-powered low-mass X-ray binary (LMXB) state and a rotation-powered radio millisecond pulsar (MSP) state. The first confirmed tMSP system, PSR J1023+0038, is currently in an LMXB state, exhibiting rapid mode switching between distinct high, low, and flaring states at X-ray, optical, and other wavelengths. Understanding the physical processes governing these mode transitions is critical for unveiling the accretion mechanisms in tMSPs and their evolutionary link to classical MSPs.
We present an analysis of J1023’s mode transitions using multiwavelength data from Kepler K2, XMM-Newton, and ground-based observations, providing new insights into the accretion flow behavior in transitional systems. Special attention is given to the high-low mode transitions, their ‘recurrence timescales’, and anti-correlation between X-ray and optical variability. By characterizing the mode-dependent flux distributions and error propagation, we provided new evidence to the mechanism driving these transitions. We further explored general changes in optical light curves before and after J1023 state transition. Optical emission was dominated by the irradiated companion star alone during radio MSP state. When the system is in LMXB state, an additional accretion disk effect should be considered. We compared the orbital modulation and concluded that the accretion disk provided more than an offset change to the optical light curves.
Our findings provide new insights into the underlying physics of tMSP state transition and moding behaviours during LMXB state, which contribute to the broader understanding of tMSP evolution dynamics.

Speaker: Pengyue Sun (the University of Manchester)

10:20 Poster Flash Presentations

Angel Castro, John Paice, Martina Veresvarska, Nabil Brice, Tom Killestein

Illuminating the Faintest Galaxies: Dwarf Galaxies as Probes of Dark Matter, Feedback, and the First Stars

Organisers: Alejandra Aguirre-Santaella, Shaun Brown, Ting-Yun (Sunny) Cheng, Jessica Doppel, Isabel Santos-Santos, Joaquin Sureda

Dwarf galaxies are the most numerous yet faintest type of galaxy in the Universe. As the most dark matter dominated systems in our Universe they offer a powerful laboratory to probe the nature of this elusive form of matter and search for potential decay signals. Their observed abundance and distribution can place strong constraints on different dark matter models.

Dwarf galaxies also serve as powerful tools for exploring the limits of galaxy formation, as they form in the smallest haloes. Their shallow potentials provide an excellent testing ground for feedback processes, such as supernovae, stellar winds, and AGN feedback. At the faintest end of the luminosity function, ultra-faint dwarfs are believed to be relics from the epoch of reionization, providing insights into the physics of reionization, the first stars, and early galaxy formation.

In the local Universe, dwarf galaxies offer the most detailed studies of stellar populations, kinematic analyses, and chemical abundances. These observations are critical benchmarks for validating and refining predictions from cosmological simulations. Upcoming facilities and surveys such as Euclid, LSST, Roman, WEAVE, 4MOST, SDSS-V, SKA, CTA and MeerKAT, will soon provide deeper and higher resolution observations for countless more dwarf galaxies, revolutionising our view of the Universe in the low-mass regime.

This session aims to foster interdisciplinary discussion and collaboration between observers and theorists working on dwarf galaxies from the classical to the ultra-faint regime. As a world leader in dwarf galaxy science the UK is well placed to fully exploit this new wealth of data.

444 The Illusion of Diversity(?): Exploring the Dynamical State of Gas Discs in Dwarf Galaxies with COLIBRE

Using hydrodynamical cosmological simulations, we show that the gas discs
of most gas-rich dwarf galaxies are not in equilibrium, challenging a foundational
assumption in rotation curve analysis. The observed diversity of rotation curves
and inner mass deficits (‘cores’) are longstanding tensions with ΛCDM predic-
tions in the dwarf regime. However, if non-equilibrium effects are “masked” by
projection and azimuthal averaging, current observational methods may create
the illusion of diversity in central mass concentration. Analysing 10^10 − 10^11M⊙
haloes from the COLIBRE simulations, and employing SPH techniques to re-
construct the (hydro-)dynamical state of the gas, we find that nearly all galaxies
in this regime are not in a steady state, with non-equilibrium effects significantly
enhanced in the inner regions. As a result, the gas rotational velocity generally
fails to trace the underlying gravitational potential, often leading to an under-
estimation of the inner mass content. Moreover, clear harmonic patterns in the
non-equilibrium component of the motions may provide a way to link them to
their physical causes, and identify them in observations.

445 The fate of Milky Way satellites: the role of halo assembly history and the dependence on subgrid physics

Dwarf satellite populations around MW-mass galaxies are closely tied to the formation and assembly history of their host haloes and central galaxies. Their abundance and properties are the combined result of continuous accretion of new satellites, disruption and merging of current satellites and numerous environmental interactions leading to quenching and morphological transformations. To explore the fate of such satellites, We use results from the PARADIGM project, a suite of zoom-in hydrodynamical simulations of MW-mass haloes evolving the same initial conditions (ICs) with two different simulation codes and galaxy formation models, VINTERGATAN and IllustrisTNG. The ICs are generated with the code GenetIC, which can perform `genetic' modifications to the ICs thus altering the formation, assembly and merger histories of a given halo in a controlled and systematic manner. Comparing between the two galaxy formation models, with their different emphases on resolved ISM and SF modelling and recovery of global observed galaxy properties, and haloes of varying assembly histories, allows us to understand what physical processes are crucial in establishing satellite populations around MW-mass haloes. We investigate how the abundance of satellites around a MW-mass halo evolves over cosmic time and over what timescales they are disrupted, and find similar trends between the two sets of simulations with satellite abundance primarily driven by halo assembly history. We also explore when and where present-day surviving satellites were quenched, finding similar populations of low-mass satellites that quenched early, mostly outside the halo, and more massive ones that quenched later and within the halo.

446 Observational evidence of star cluster migration and merger in dwarf galaxies

Nuclear star clusters (NSCs) are the densest stellar systems in the Universe. They can be found at the center of all galaxy types, but tend to favor galaxies of intermediate stellar mass around one billion solar masses, i.e. in the regime of dwarf galaxies. Currently, two main processes are under debate to explain their formation: in-situ star-formation from gas infall and migration and merging of globular clusters (GCs) caused by dynamical friction. Studies of NSC stellar populations suggest that the former predominates in massive galaxies, the latter prevails in dwarf galaxies, and both contribute equally at intermediate mass. However, up to now, no ongoing merger of GCs has yet been observed to confirm this scenario. In my talk, I present the discovery of five dwarf galaxies with complex nuclear regions, characterized by multiple nuclei and tidal tails, using high resolution images from the Hubble Space Telescope (Poulain et al. 2025, Nature). These structures have been reproduced in complementary N-body simulations, supporting the interpretation that they result from migrating and merging of star clusters. The small detection rate and short simulated timescales (below 100 Myr) of this process may explain why this has not been observed previously. This study highlights the need of large surveys with high resolution to fully map the migration scenario steps.

Speaker: Oliver Müller (EPFL & University of Cambridge)

447 Globular Clusters as Probes of Galaxy Evolution: Insights from Ultra-Diffuse Galaxies

Globular clusters (GCs) are valuable tools for studying the formation and evolutionary history of galaxies. As old (t > 10Gyr) and relatively simple stellar systems, they act as fossil tracers and can be used to disentangle the processes that have shaped galaxies within their host environments. On extragalactic scales, GCs are typically unresolved bright sources, and their properties are studied through integrated light observations. By analyzing the color, luminosity, and spatial distributions, total number, and kinematics of globular clusters, we can uncover critical information about the environment and star formation history of their host galaxies, their past interactions, and dark matter content.
In the last decade, deeper imaging data have led to the identification of a new subset of extremely low-surface brightness galaxies, known as ultra-diffuse galaxies (UDGs). The formation mechanisms of these galaxies remain enigmatic. Their many puzzling properties–including stellar mass, dark matter mass and globular cluster abundance–suggest that multiple formation pathways may be at play. One way to discriminate between different formation scenarios is through the study of the GC populations within these galaxies. During my talk, I will present results about our study of the GC population in UDGs in the Hydra I cluster. These results are derived by combining the spectro-photometric
capabilities of data obtained with MUSE@VLT in synergy with near-infrared observations taken with VIRCAM@VISTA.

09:56 Poster Flash Presentations

10:02 Discussion

Solar System Insights from Small Body Populations

Organisers: Abbie Donaldson, Alan Fitzsimmons, Charlotte Götz, Agata Rożek, Colin Snodgrass

The formation and migration history of the Solar System is encoded in remnant planetary disc material, known to us as the diverse populations of minor planets. These objects make compelling and informative targets for spacecraft encounters, and in recent years major scientific advances have been possible with data returned by missions such as DAWN, Rosetta, and New Horizons. A host of current and upcoming missions will further revolutionise our understanding of the Solar System’s structure and history e.g. the characterisation of numerous Jupiter Trojans by the Lucy flybys, the Hera mission to assess the Didymos-Dimorphos system following the DART impact, and the first ever up-close study of a dynamically new comet by Comet Interceptor.

Our ability to characterise small bodies remotely is also rapidly improving. JWST and powerful ground-based facilities can now probe the compositions of objects and their atmospheres from near-Earth space through to the trans-Neptunian region. The imminent Legacy Survey of Space and Time will discover millions of small bodies across the entire Solar System, providing long-term monitoring and capturing transient events like activity and collisions. The ability of the forthcoming 39-m ELT to characterise distant Solar System objects will be entirely unprecedented. This wealth of observed properties will inform current and new theoretical models of planetary formation and evolution.

In this highly exciting time for small body science, we welcome presentations from researchers working on any and all minor planet populations including relevant missions, new observations, or theoretical studies.

448 Using ground-based IFUs to constrain cometary activity drivers

The last decade has seen the advent of large field of view Integral Field Spectrographs (IFUs) for observations at optical wavelengths. These instruments, such as MUSE on the 8-m Very Large Telescope, present an interesting opportunity to characterize the distant activity of comets, due to the combination of spatial and spectral information they provide. Large scale IFUs on ground-based telescopes can be particularly useful to probe cometary activity drivers that are typically difficult to measure from the ground, including H$_2$O, CO, CO$_2$- and potentially O$_2$ - through the study of some of their dissociation products such as oxygen. IFUs are generally very sensitive to faint extended emission and are thus ideal tools for the observations of active small bodies in the solar system. This talk will explore how IFUs can contribute to our understanding of the distant activity of small bodies by mapping forbidden oxygen lines and how future IFUs on even larger telescopes will likely push this opportunity even further.

449 Probing Cometary Extended Sources from VLT/MUSE

Following ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P) from 2014-2016, we conducted hyperspectral observations with the Very Large Telescope’s (VLT) Multi-Unit Spectroscopic Explorer (MUSE) instrument during its 2021–2022 apparition. These observations span two seasons on 67P, and perihelion, enabling simultaneous mapping of the dust coma and gaseous species evolution, specifically: [OI]$^1$D (a proxy for H$_2$O), C$_2$, NH$_2$, and CN. We identify two dominant regimes in the coma's morphological evolution: (1) variable [OI]$^1$D and C$_2$ structures linked to nucleus-driven sublimation, and (2) more stable NH$_2$ and CN emissions associated with seasonal illumination, known dust structures, and likely extended sources. To explore the existence of extended sources, we applied radial Haser modeling on NH$_2$ and CN profiles, and computed spectral reflectivity maps from the dust coma. Pre-perihelion NH$_2$ from 67P’s north pole shows 1.5–1.9× longer effective photochemical scale lengths when compared with the rest of the coma, consistent with partial extended source production. Additionally, CN emission in the south coincides with a known dust fan whose spectral slope is 2–3× redder than the surrounding dust coma, suggesting the presence of larger or more organic-rich grains that may act as extended sources and contribute to CN production. This analysis serves as the foundational work for the broader MUSE comet survey, which includes over 30 comets spanning diverse heliocentric distances and dynamical classes. We aim to explore and compare the gas and dust morphologies for these comets, such that a deeper understanding of extended sources and their roles in comet comae can be ascertained.

Speaker: Mr Brian Murphy (University of Edinburgh)

450 Tracking Cometary Rotation and Morphology with Narrowband Imaging

This study presents findings from narrowband imaging of comet C/2006 P1 (McNaught) using the 3.6-meter New Technology Telescope (NTT) at La Silla, Chile. Observations commenced on January 27, 2007, 15 days after perihelion, and continued until February 4, with additional sessions from February 25 to 28. Imaging was conducted using the ESO Multi-Mode Instrument (EMMI) in both broadband (BV R) and six comet-specific narrowband filters (CN, C3, C2, NH2, blue, and red continuum). Various image processing techniques were employed to enhance structural features, including azimuthal mean/median profile subtraction, azimuthal renormalization, and division by a 1/ρ profile. These enhancements revealed dynamic coma structures, with jets transitioning from spiral patterns to linear or fan-like shapes over time. The consistency of morphological patterns across different processing methods confirmed their authenticity. The periodic recurrence of coma features in CN narrowband images allowed for the estimation of the comet’s nucleus rotation period. Time-series morphological analysis using two techniques, root mean square (RMS) and angular feature tracking in the coma were used to find temporal variations across two observing epochs, indicating a rotation period consistent with the observed morphological changes. The RMS analysis identifies minima suggesting a rotation period of the comet's nucleus of 11.3±0.5 hours, while time-resolved angular tracking of coma jets indicates a rotation period of about 5.65±0.3 hours, which is a factor of two.

451 Kalliope: Discovery of the first metallic asteroid family

In the classical theory of planetesimal differentiation, a body would form an iron-rich core, an olivine-dominated mantle, and a pyroxene-rich basaltic crust. The detection of differentiated bodies in the current asteroid main belt will allow us to get insights and study the very initial phases of planetesimal accretion.

Asteroid (22) Kalliope is the densest known asteroid with ⍴=4.4±0.46 g.cm-3 indicating a metal-rich composition. The low radar albedo (0.18±0.05), however, points towards a lower metal content on the surface but the presence of very high density indicates a differentiated metal-rich interior.

(22) Kalliope is the parent body of an asteroid family in the outer main belt consisting of 302 members. Therefore, studying the physical properties of the Kalliope family members we can get insights into the internal structure of the original planetesimal.

Thirty seven Kalliope family members have visible reflectance spectra from Gaia DR3 and 22 of which were observed at NASA IRTF obtaining their near-infrared spectra. Using the reflectance spectra of Kalliope family members as well as their geometric visible albedos we matched them with meteorites that are included in the RELAB and PSF meteorite lab spectra databases.

We discovered that the Kalliope family is the first family that consists of metallic and stony-metallic fragments, confirming the differentiated nature of the original planetesimal.

452 Search for ancient asteroid families in the pristine zone

The size distribution of early solar system planetesimals remains poorly understood. Accurate knowledge of this size distribution is crucial for developing more sophisticated solar system formation models. Asteroids are fragments of primordial planetesimals that broke off during collisional events, forming asteroid families, or are surviving planetesimals themselves. By identifying and accounting for all asteroid families, we can begin to assess the surviving planetesimal population.

The current asteroid family catalogs are created using hierarchical clustering method (HCM). However, HCM is known to be ineffective for very old and dispersed asteroid families. In this study, we try to detect another signature of asteroid families, namely the Yarkovsky V-shape, to search for ancient asteroid families.

We focus on the pristine zone of the main asteroid belt (2.82-2.96 au) as this zone is thought to preserve the original planetesimal population better and the existing asteroid families in this region are well identified. We also account for the halos of known families using V-shape constrained HCM to obtain a cleaner background. When looking for V-shapes among the dark bodies (albedo < 0.12), we identified a possible V-shape signature for an asteroid family that could have formed ~4Gy ago. This is possibly the third such ancient asteroid family to be discovered in the main asteroid belt.

Speaker: Ullas Bhat (University of Leicester)

453 Asteroid contact binaries in optical and radar observations

Bi-lobed objects (contact binaries) consist of between 15-30% of near-Earth objects (NEOs) and also appear in the main asteroid belt, Kuiper belt, and comet populations. Notable contact binaries include Itokawa - visited by the Hayabusa mission, Selam - visited by the LUCY mission, and 67P which was visited by the Rosetta mission. We use archival radar observations in combination with optical lightcurves to constrain the spin states of a small selection of these objects and create detailed shape models using the SHAPE modelling software. Radar observations are crucial for modelling the neck structure and any other concavities or craters on the surface of the objects, as optical observations are not sufficient to unambiguously reproduce details such as depth or shapes of such features. Radar observations, however, can contain shape and distance observations to resolutions down to only 2.5 meters. From these models, we can estimate the objects' sizes, bulk and surface densities, and physical compositions. This allows us to make inferences on their possible formation histories and scenarios for how they might have evolved, and better characterise the different types of contact binaries that we observe. We are creating several of these shape models using radar data from both the Goldstone and Arecibo observatories to investigate any notable similarities or differences between these asteroids.

Speaker: Richard Cannon (University of Edinburgh)

454 The Galactic Interstellar Object Population in the LSST

Interstellar objects (ISOs) are physical samples of distant planetary systems, forming a Galaxy-spanning population, constantly streaming through the inner Solar system for us to study. In preparation for the imminent completion of the Vera C. Rubin Observatory, an ongoing targeted precursor survey on CFHT and the upcoming launch of the NEOSurveyor mission, we present a novel simulation of ISO discoveries in the LSST. We combine the Ōtautahi-Oxford model of the local ISO chemodynamical population, a novel method of efficient orbit sampling and detailed observability criteria to estimate the discovery biases that will be present in the Rubin ISO sample. Our predictions show that the LSST will find 6-51 ISOs over 10 years, and with just a few discoveries we will be able to significantly constrain the size distribution slope. We further find that the discovered sample of ISOs will show a slight bias towards slower-moving objects and distinct biases in certain orbital parameters, however crucially the predicted complex velocity space structure will still be apparent and the discovered sample will be unbiased in composition and age. This means the Rubin ISO sample can be used to test models of planetesimal formation, Galactic evolution, and tidal stream formation.

455 Characterising Comets in the LSST Era: Preparing for Comet Interceptor

The formation and migration history of the Solar System is encoded in remnant disc material. Comets are small, kilometre-sized planetesimals and as such are best characterised in situ. Only short period comets have thus far been studied by space missions - by nature, these comets have evolved substantially throughout repeated perihelion passages in the inner Solar System, where temperatures are sufficient to deplete their volatiles and erode their surfaces. It is challenging to reconcile the properties of the original disc material from such thermally processed objects.
The Comet Interceptor (CI) mission will be the first to encounter a comet making its first passage into the inner Solar System. As such objects are typically discovered ~years before perihelion, CI will wait in orbit until a suitable target has been identified. The upcoming Legacy Survey of Space and Time will survey the entire sky with a limiting magnitude of ~24, discovering thousands of new comets. Our priority before the survey begins is to determine the likelihood of identifying a mission target during CI’s operational window with sufficient lead time for mission planning purposes. We will present preliminary findings using the ‘Sorcha’ simulation package combined with newly-developed empirical long period comet brightening models to simulate expected detections with LSST.

Crossing Boundaries: The benefits of ArtScience for contemporary astronomy research

Organisers: Ulrike Kuchner, Soheb Mandhai; co organisers: Jenni French, John Paice, Jake Noel-Storr, Houda Haidar

Art and science both expand human knowledge by blending imaginative thinking with analytical decision-making to create original ideas. Despite their historical synergy, fully harnessing their potential in today’s astronomy research is challenging. Ever-growing data, large-scale collaborations, and the rise of artificial intelligence often limit opportunities for creative engagement with complex ideas and data. Artistic methods like virtual reality, music, digital and performance art, offer inclusive ways for exploration, understanding and communication.

While art is widely used for information visualization in outreach and science communication, this session focuses on three less-explored aspects of ArtScience:

o Creativity: ArtScience to contribute to knowledge creation will provide an overview of research and practice into ArtScience for interdisciplinary goals (eg. Kuchner+2023; Birsel+2023).
o Inclusivity: ArtScience to improve research culture and accessibility will highlight artistic methods and tools promoting equality, inclusivity, and diversity (eg. Sensory science clubs for neurodiverse audiences).
o STEAM: ArtScience to support teaching and learning will share STEAM (STEM+Art) practice for education (eg. Aguilera+2024).

We will address key challenges, such as navigating differing disciplinary practices, finding funding, and contextualizing collaborative outcomes. Practical advice will include available UK funding schemes, joining communities, setting shared goals, and evaluating results.

456 From experience to evidence: Making the case for meaningful interaction across art and science

Art and science share a common goal: to challenge our understanding of reality. Both are human pursuits aimed at making sense of the complex world we inhabit and our role within it. As a creative crossroads, the contemporary field of ArtScience — whether through collaboration or individual practice — has been gaining momentum in recent years. However, uniting these disciplines remains a bold and ambitious challenge.

Rooted in their own distinct traditions and specialisms, collaborations between art and science often face barriers. Art in these partnerships is frequently seen as a tool for communicating complex scientific ideas, rather than as a fundamental contributor to scientific discovery. This is surprising given the unique psychological relationship humans have with art: experiencing art can foster understanding, meaning-making, and the generation of new ideas, all of which are essential for tackling complex problems and driving creativity in research.

In this talk, I will explore why collaboration between art and science is so valuable and what it takes to achieve successful co-creation. I will highlight two distinct models of ArtScience collaboration: one emerging from within a university setting and another developed as a globally self-organized collective.

First, I will share insights and examples from ARTlab, our experimental, research-driven ArtScience space at the University of Nottingham, which has hosted nine artists-in-residence and led to the major Cosmic Titans exhibition, along with significant research outputs. Then, I will spotlight the work of SEADS (Space, Ecologies, Art, and Design), a global collective pioneering ArtScience practice beyond institutional boundaries.

457 Sensing the Universe: Visualisations in Cosmology

This presentation paper will take as it’s starting point a three-way conversation about visualisations in cosmology that I had with Professor Mark Swinbank and the late Professor Richard Bower - both of the Institute of Computational Cosmology (ICC) at Durham University. The exchange was part of my Leverhulme Fellowship, 'Material Sight: Re-presenting the Spaces of Fundamental Science' 2016-18 that examined the cognitive and imaginative challenges that fundamental science and technology pose, especially for non-scientists.

Our conversation tracked the differences between visualisations that are built from astronomical observations on the one hand and simulations constructed from cosmological data on the other. I was interested in how these differences played out in relation to one of the central critical tenets within my own field - namely, photography’s indexical relationship to the world. In other words, photography as a trace, like a footprint, that denotes ‘this has been’ and connects us to time and space.

Expanding from this starting point, I will show the filmwork installation 'Boulby/Hubble' 2018 that came from the collaboration with Swinbank and Bower at the ICC and that, along with the wider research from 'Material Sight', attempts to connect us sensorially to remote environments.

(Crisp is an artist and is Professor of Contemporary Art at Northumbria University, Newcastle where she co-leads 'The Cultural Negotiation of Science' research group. Her work is represented by Matt’s Gallery, London and is held in several national collections including The Tate, Arts Council Collection, British Council Collection, Government Art Collection and the National Trust.)

458 Bioart in space: Ontological existential dimension of the biocentered experience of space

Bioart in Space: Ontological-Existential Dimensions of a Biocentered Experience of Space explores the ontological distinction between technologically mediated and biologically centered experiences of space. This presentation investigates how the nature of experience itself can become a foundational question for organizing both the conceptual and material frameworks of artistic practice in outer space. Through the analysis of key projects by Luis Guzmán—Bioarchitecture CosmoEcology (2020–2025), The Angel of History (2025), and Migrante/Alienígena (2025)—the talk will trace the development of a multi-scalar exploration of the cosmos. Guzmán will articulate the philosophical, material, and technological dimensions of his work, positioning biology not only as a medium but as a mode of being-in-space.

459 Earth, a Cosmic Spectacle

Louise will share her 2024 British Council funded project, ‘Earth, a Cosmic Spectacle’ which was developed in collaboration with astronomer Dr Ian Griffin and Tūhura Otago Museum in Aotearoa New Zealand. In this project, the artist invited astronomers, biologists, and geologists to gaze into the dark skies of New Zealand and anonymously write a letter exploring how their knowledge of Earth's long and gradual development, starting from the dawn of the Universe, shapes their understanding of the cosmic significance of the climate crisis.

https://www.louisebeer.com/work#/earth-a-cosmic-spectacle-images-aotearoa/

Louise will also discuss her chapter ‘The Transparency of Night’ (https://www.taylorfrancis.com/chapters/oa-edit/10.4324/9781003408444-6/transparency-night-louise-beer?context=ubx&refId=9a0efecb-7e5b-4d7f-86c7-ce70e207dba3) which she contributed to Dark Skies: Places, Practices, Communities, edited by Tim Edensor and Nick Dunn and published by Routledge in late November 2023. The abstract is below:

As light pollution increases around the world, humanity is losing a symbolic visual connection to the cosmos, shared by our ancestors throughout history. The author examines how living under the dark skies of Aotearoa, New Zealand, has influenced her artistic and curatorial practice and how her artwork can invite the audience to explore their own changing relationship with the night. Through the discussion of five artistic projects, this chapter explores how living under dark skies, or light-polluted skies, can change our perception of grief, the climate crisis, and Earth’s deep-time history and future. Each of the projects has started with a fundamental connection to the night sky and reflects the author’s changing understanding of life, death, darkness, and light.“

09:50 Poster Flash Presentations

460 Listening to the Universe: Harnessing Sound for Inclusive Astronomy Communication

We are all blind to the Universe, yet traditionally astronomy communication relies on visual representations, which are not accessible to those who may need or prefer non-visual methods. Audio Universe is a collection of tools and resources to support data analysts, educators, and communicators to represent data and concepts with sound (data sonification). Working with educators, students, musicians, and astronomers (including members of the Blind and Vision Impaired (BVI) community), we have created an immersive planetarium show, Tour of the Solar System, which uses sound to represent objects in the Solar System. Our evaluation demonstrated great success: both BVI and sighted audiences found the sounds enjoyable and useful. Additional feedback from communication leaders revealed the multi-sensory nature made it successful with audiences with broader special educational needs (SEN). Based on this success we are now developing a Sonification Toolkit, working with planetaria and science communicators/educators across the UK, which will enable them to create bespoke educational resources using sonification. I will present what we have learnt from working with SEN groups at the National Space Centre using audio and tactile resources, as part of the development of this Toolkit. Using multisensory resources increases the variety of ways to engage in astronomy making the field more inclusive and open to new audiences who may previously have felt excluded, and as a result we all benefit from shared knowledge, and the wonder of the Universe.

Speaker: Rose Shepherd (Newcastle University)

461 Bridging the Cosmos: Fostering Equity and Inclusion through Art and Creativity in Astronomy Research

This talk will explore the transformative potential of integrating art and creativity into astronomical research to foster equity, diversity, and inclusion among professionals within the field. Drawing on interdisciplinary approaches that have successfully enhanced inclusive engagement in scientific endeavours (Wright et al., 2023), we examine how arts-connected research methodologies can challenge conventional paradigms (Smith, 2014). The presentation will illustrate emerging practices from art–science collaborations that highlight diverse perspectives, revealing novel epistemological frameworks informed by creative methodologies (Chilton & Leavy, 2020). The talk will show how artistic practices not only enrich data visualization, interpretation and understanding but importantly move to amplify and equalise the volume of historically underrepresented voices within the astronomical community. Ultimately, this exploration advocates for a rigorous, creativity-inflected research agenda that leverages artistic and creative dynamics as a catalyst for more inclusive and equitable scientific practice in astronomy.

462 Accessibility in Communicating Science

Science communication enables researchers to share their researched and reach wider audiences through conferences, news articles, public engagement, and seminars. It is a vital part of our jobs, and should be considered important. Unfortunately, a lot of science communication is inaccessible. 10% of the population have some form of dyslexia and 8% of men experience colour-blindness, making many resources difficult to access fully. People with chronic migraines, head injuries and chronic fatigue also struggle to fully engage with inaccessible presentations and articles. Where we rely on figures and presentations to relay our research, designing them in an accessible manner is a requirement. I will provide a quick best-practice crash course on practical and simple ways to improve accessibility while communicating science, focusing on colour choices for figures and posters, font choice, and best design practices to make our research more readily available to all. I will share several free resources that ensure making science communication accessible is not a laborious process.

463 Elevate Your Slides: The Power of Artistic Vision in Scientific Presentations

Ever sat through a talk packed with interesting science but struggled to stay engaged? You're not alone. Good science can easily get lost behind complicated slides. This session we will explore how taking a creative and artistic approach in your scientific presentations can significantly make your talk more engaging and memorable. We'll discuss common slide pitfalls, and explore simple, practical ways to improve your visuals, colour schemes, and storytelling (no fancy art skills required!). Join in to see how thinking creatively can help you better connect with your audience and leave them just as excited about your science as you are!

Euclid science exploitation in the UK

Organisers: Stephen Eales, Alex Hall, Mathilde Jauzac, Christopher Lovell, James Nightingale, Francesco Shankar

Euclid launched on July 1st 2023, and is the European Space Agency’s flagship dark energy mission, mapping the large scale structure of the Universe. Although primarily a cosmology mission, Euclid is expected to be a transformative survey for many different areas of astronomy, including exoplanets, galaxy evolution, and transients. The UK has made significant investments in Euclid, and there is now a large community of researchers either working in the Euclid Consortium or planning to make use of Euclid data.

After the release of the first images, the next outstanding milestone for Euclid will be the first public data release (Q1) around March 2025. The Euclid consortium is now actively working on producing a number of papers that reflect the rich variety of science that can be derived from Euclid data.

This NAM session is dedicated to showcasing how UK researchers are using Euclid data for world leading science, and synergies with other key surveys. The session will also include review talks on the key science areas of Euclid (weak lensing, galaxy clustering, and legacy science), as well as a number of contributed talks from Euclid consortium members and external users. Finally, it will also be an opportunity to look forward to data release 1 (DR1) in 2026, and the exciting science enabled by this next batch of Euclid data.

464 WEAVE/StePS-Euclid synergy and first Euclid emission line maps

In this talk, I will explore the promising synergy between WEAVE/StePS and Euclid for studying dust attenuation in the COSMOS field. The well-constrained ratios of intrinsic hydrogen emission lines provide a robust method for measuring wavelength-dependent dust attenuation, which is crucial for accurate flux corrections and reducing biases in the estimation of physical parameters of galaxies (e.g., Star Formation rates). By combining high-resolution WEAVE spectra (0.36 to 0.96 μm, R > 5000) with Euclid's low-resolution near-infrared spectra (R > 380) from its blue (0.92–1.30 μm) and red (1.25–1.86 μm) grisms, we achieve comprehensive spectral coverage, capturing Balmer and Paschen hydrogen emission lines (Hβ, Hα, Paschen β, and Paschen γ) in star-forming galaxies at 0.3 < z < 0.7. I will discuss the powerful possible cross-calibration between the two spectrographs, highlighting the challenges of integrating data from different instruments, particularly when one is slitless and the other fiber-based. Additionally, I will present how these efforst led me to work on the first Euclid emission line maps and will present some of them in the talk. These maps are essential for ensuring consistency between WEAVE and Euclid measurements.

465 Weak lensing cosmic shear measurement in the era of Euclid

We are now well into science operations with Euclid and are preparing for internal DR1 expected late this year. In order to measure cosmological parameters with 1% precision via the weak lensing by the large scale structure, we need to measure the 1% coherent distortion of galaxy images, cosmic shear, over 2,500 sq. deg. for DR1 with exquisite accuracy. However, we also have to control the systematic errors impacting the measurement. In my talk I will review the results from the work I am leading: pre-launch data, early release images (Abell 2390), and Q1 data. This is all in preparation for the much larger data volumes in the months to come.

466 The active galaxies of Euclid

The first public data release of Euclid provides a glimpse into the superb capabilities of its instruments across all of astrophysics. In this talk, I will present the first catalogue of candidate active galactic nuclei (AGN) in the Q1 fields across 63 sq. deg. We created a multi-wavelength catalog combining GALEX, GAIA, DES, WISE, Spitzer, and DESI data. We find a total of 229,779 AGN candidates across all selections, equivalent to an AGN surface density of 3,641 sq.deg. for 18<I<24.5, and a subsample of 30,422 candidates corresponding to an AGN surface density of 482 sq.deg. when limiting the depth to 18<I<22. The surface density of AGN recovered from this work is in line with predictions based on AGN X-ray luminosity function predictions. I will also discuss future prospects, anticipating the upcoming first data release covering about 2,000 sq.deg.

Speaker: Sotiria Fotopoulou

467 A first census of dwarf galaxies and tidal features in Euclid Q1

ESA’s Euclid satellite offers an exceptional combination of high spatial resolution, wide field-of-view, and a stable point spread function (PSF), making it ideal for exploring the Low Surface Brightness (LSB) Universe. The Early Release Observations (EROs) offered remarkable insights into LSB structures, while the Quick Release 1 (Q1) data, spanning 60 square degrees, provides unprecedented opportunities to explore the faint regime. Dwarf galaxies and tidal features resulting from galaxy mergers are particularly suited for such studies, allowing for their characterisation across a range of environments and galaxy properties.

In this talk, I will present a census of dwarf galaxies identified in the Q1 data using a semi-automated selection approach. We investigated their morphologies, distances, masses, and spatial distributions. Additionally, I will share preliminary results on the quantitative characterisation of tidal tails in ongoing galaxy mergers. We compiled a catalogue of tidal features around galaxies in the Local Universe, and I will discuss how these properties correlate with the mass and environment of the host galaxies.

As the properties of the Q1 data closely resemble those of DR1, both studies serve as valuable testbeds for developing scalable methods in preparation for the next data release. For instance, as visual inspection will not be feasible for DR1, our catalogues of dwarf galaxies and tidal features serve as valuable training datasets for deep learning algorithms, enabling automated detection of faint structures in future Euclid data releases.

468 Discovery of bright z=7 galaxies in UltraVISTA and Euclid COSMOS

We present a search for $z\simeq7$ Lyman-break galaxies in the COSMOS field using the $1.72 \ \rm{deg}^2$ near-infrared UltraVISTA survey. We incorporate deep optical and Spitzer imaging for a full spectral energy distribution (SED) fitting analysis. We find 291 candidate galaxies at $6.5\leq z \leq 7.5$ covering $-22.6 \leq M_{\rm{UV}} \leq -20.2$, faint enough to overlap with Hubble studies. A separate selection including complementary Euclid performance verification imaging in the SED fitting yields 141 galaxies in $0.65 \ \rm{deg}^2$. In the higher resolution Euclid imaging, $\sim18$ per cent of the sample show irregular/clumpy features. We compute the rest-frame UV luminosity function (LF) from our samples, extending to below the knee ($M^*\simeq-21.1$). We find that the shape of the rest-UV LF is consistent with previous findings of a double-power law at $z\simeq7$. The UltraVISTA+Euclid sample provides a cleaner measurement of the LF due to the overlapping near-infrared filters identifying molecular absorption features in the SEDs of brown dwarf interlopers. A comparison with JWST LFs at $z>7$ suggests a gentle evolution in the bright-end slope, although this is limited by a lack of robust bright-end measurements at $z>9$. We forecast that in the Euclid Deep Fields, the removal of contaminant brown dwarfs as point sources will be possible at $J \lesssim 24.5$. Finally, we present a high-equivalent-width Lyman-$\alpha$ emitter candidate identified by combining HSC, VISTA, and \euclid broadband photometry, highlighting the synergistic power these instruments will have in the Euclid Auxiliary Fields for identifying extreme sources in the Epoch of Reionization.

469 Searching for strong lenses in Q1 with Machine Learning

Euclid’s space-based resolution over a third of the sky makes it the perfect tool for finding strong gravitational lenses, being expected to increase the total number by two orders of magnitude. To find strong lenses in the Euclid Q1 data, I repurposed the Zoobot machine learning model that was pretrained on GalaxyZoo morphologies. In combination with 4 other machine learning networks, we searched for strong lens candidates in Q1, which we validated with human visual inspection. This resulted in our discovery of 500 strong lenses. The finetuned Zoobot model shows a substantial improvement in purity over previous lens searches, with 160 strong lenses in the top 1000 ranked images - a testament to the power of transfer learning. Although scaling up visual inspection is challenging, I will demonstrate how iterative machine learning training, where a network can learn from its mistakes, is able to further increase lens-finding performance. This is essential for finding the ~100,000 strong lenses in the full Euclid Wide Survey, which will facilitate significant advancements in our understanding of cosmography, galaxy formation, and dark matter.

470 The FornaX XMM Heritage Programme

At the end of 2023, an X-ray XMM Heritage programme of 3.6 Ms was allocated to perform a deep uniform survey of the 10 deg^2 Euclid Deep Field Fornax. More than 500 low-mass X-ray clusters will be detected out to a redshift of 2. We present the progress of this ongoing XMM campaign and plans for the Euclid DR1 release. The exceptional multi-wavelength data set to be obtained on this field will allow us to trace back the joint X-ray optical/IR properties of the galaxy group population, along with the evolution of AGN activity. Comparing detailed joint instrumental simulations of the X-ray and optical catalogues for the Wide and Deep Euclid surveys will provide a unique understanding of the Euclid cluster selection function. In this way, the sources of systematic uncertainties in the cosmological analysis of the Euclid clusters will be clarified.

471 Probing Ultracool Atmospheres with ATMO2020 and Euclid Spectrophotometry

Ultracool Dwarfs (UCDs) are faint, low luminosity objects that span the stellar-substellar boundary, encompassing the lowest-mass stars and brown dwarfs. The Euclid mission will uncover many hundreds of UCDs thanks to its wide coverage and deep sensitivity. To most completely characterize a Euclid UCD the wide wavelength coverage of the Euclid optical and near-infrared photometry should be combined with the low-resolution near-infrared spectrum. In this study we use the ATMO 2020 atmosphere models to assess how we can constrain atmospheric parameters such as effective temperature, surface gravity and metallicity from Euclid spectrophotometry. We use these models to simulate a typical Euclid UCD dataset, and then perform Monte Carlo simulations with randomly generate Gaussian noise to fit our atmospheric model grid to our simulated dataset. We explore how best to weight the photometric and spectroscopic data points in our model fitting simulations, and determine the signal-to-noise required to most accurately determine the atmospheric parameters. Finally, we perform our model fitting on a real Euclid dataset of a T7 type brown dwarf, providing constraints on its effective temperature, surface gravity and metallicity.

Revealing the Milky Way with Gaia: Focus on Galactic dynamics in the Gaia era and beyond

Organisers: Paula Gherghinescu, Nicholas Walton; co organisers: Sioree Ansar, Giorgia Busso, Nigel Hambly, Jason Hunt, Sophia Lilleengen, Nicholas Rowell, George Seabroke, Mark Taylor

The ESA Gaia mission is creating a 3-D map of over two billion stars in our Milky Way. Gaia continues to provide new insights into our understanding of the Milky Way. In particular, the field of Galactic dynamics is an example of study that has been revolutionized with the availability of data from the Gaia mission.

It is now possible to directly map the structure and kinematics of all major Galactic components to unprecedented detail and precision. However, many traditional dynamical modelling methods use the Jeans theorem and start by assuming the galaxy is in dynamical equilibrium and axisymmetric.

While these models continue to be valuable in offering a’ big picture’ view up to large scales, their underlying assumptions can describe our Milky Way to first order only. For example, prominent non-axisymmetric structures such as the bar and spiral arms influence the dynamics of stars far across the disc, while the phase spiral (first revealed in the Gaia DR2 data), the warp, and the perturbation induced by the LMC in the outer halo highlight departures from equilibrium both locally and on the largest scales.

Current models do not fully capture the complexity of the data. With the increase in quantity and quality expected from Gaia DR4 and DR5 (supplemented with data from Euclid, LSST, and more) improved modelling methods are required.

The session will begin with an update from the Gaia:UK project team describing the latest scientific and technical performance of Gaia, developments in Gaia data acess, and giving a look ahead to the rapidly approaching seminal release of Gaia DR4, the full release of the 5 year Gaia nominal mission.

It will then focus more specifically in bringing together researchers working on a variety of novel numerical and analytical tools, as well as expertise in Gaia and associates survey data, to address challenges in improving our modelling techniques. Half block sessions will cover on (a) features and dynamics in the disc, (b) the dynamics of the halo, and (c) the Milky Way in a cosmological context.

09:00 Prep time

472 The Gaia Mission: Science, Status and Upcoming Data Releases

This presentation will provide a brief update on the ESA Gaia mission status, reflecting that whilst inflight operations ceased with the recent (27 March 2025) 'passivation', the mission continues with current activity focused on the generation of Gaia Data Release 4 (Gaia DR4) scheduled for later in 2026.

Gaia DR4 will see a significant number of new data products being made available to the community, essentially full epoch astrometry, (speoctro)photometry, spectroscopy and derived products (e.g. astrophysical parameters) for all processed sources, some 2.7 billion in total.

I will discuss the contents of Gaia DR4 and give a look ahead to Gaia Data Release 5. The presentation will also cover a number of recent mission highlights and key science results, noting the contribution of the Gaia UK team and wider UK research community.

473 Gaia data access facilities

Various tools and methods (web GUIs, client applications such as TOPCAT, client-side programmatic APIs, and code-to-data platforms such as the UK Gaia Data Mining Platform and ESA DataLabs) currently available for science exploitation of Gaia data releases will be summarised. Illustrative examples employing Gaia DR3 will be shown. Facility developments will be described in the context of a look-ahead to Gaia DR4 which will feature a huge expansion in released data products.

Speaker: Nigel Hambly (University of Edinburgh)

474 Gaia-Sausage-Enceladus merger induced thick and thin disc transition revealed by APOGEE and Gaia

Tracing the Milky Way disc structure as a function of stellar age is key to understanding its formation history. However, fitting density models to observational data is a major challenge due to selection biases.
To avoid modelling the complex selection function, we focus on fitting stellar kinematics, using the quasi-isothermal disc distribution function. We use the APOGEE DR17 giant stars, with ages estimated from BINGO, an asteroseismology trained Bayesian Machine Learning framework (Ciucă et al. 2024, MNRAS, 528, L122), and crossmatch them with the Gaia DR3. We estimate how the scale length and radial/vertical velocity dispersions change with age by fitting a non-parametric spline function.
Our results show that the old (>~10Gyr) stellar disc has a small radial scale length (1.8 kpc) and high velocity dispersion, consistent with expected properties of the thick disc. In contrast, the young (<~8 Gyr) disc shows an increasing scale length and decreasing velocity dispersion with decreasing age, supporting an inside-out and upside-down formation scenario for the thin disc. Notably, this transition between the thin and thick discs coincides with the end of the Great Galactic Starburst, which is thought to be linked to the Gaia-Sausage-Enceladus (GSE) gas-rich merger (Ciucă et al. 2024). We also find a slight decrease in scale length at this transition epoch, consistent with the aftermath of a GSE-like gas-rich merger seen in simulations of Grand et al. (2018, MNRAS, 474, 3629). This suggests that the GSE merger may have triggered the transition from thick to thin disc formation phase.

Speaker: Natsuki Funakoshi (MSSL, UCL)

475 The disturbance(s) of the outer Milky Way disc

One of the most striking things that we have learned about the Milky Way from Gaia data is the extent to which its disc has been disturbed. The way we describe and characterise this disturbance seems to depend on how we are looking at it. We can at least agree that the Milky Way’s disc is rippling up and down, and a prime suspect for this disturbance is the Sagittarius dwarf galaxy shaking the disc as it passed by some time ago.

In this talk I will focus primarily on the outer Milky Way disc, and show how this disturbance can be seen here.  I will present new work on the Milky Way's warp which shows that the position and kinematics of stars in the warp are inconsistent with the picture of a simple precessing warp. I will also show how there is a break of the velocity distribution into two clumps: one rotating slower around the galactic centre and moving downwards, and one rotating faster and moving upwards.  I will show how these behaviours are replicated in simulations of the impact of the Sagittarius dwarf on the Milky Way disc, and argue that these disturbances will allow us to conduct ’Galactic-seismology’ and determine the structure and history of the Milky Way with new clarity.

Speaker: Paul McMillan (University of Leicester)

476 Signatures of bar-driven radial migration in the Milky Way disc

Radial migration—a process that moves stars from their birthplaces to their present-day galactocentric radii—has been shown to play a crucial role in shaping the Milky Way disc, particularly based on age and metallicity measurements of stars in the solar neighbourhood. With Gaia DR3, we now have chrono-chemo-kinematic maps of the Milky Way that extend far beyond the solar neighbourhood, enabling us to distinguish between different radial migration mechanisms.

In this study, we focus on the observational signatures of radial migration driven by the expansion of the bar’s corotation resonance as the bar slows. Using a test particle simulation, we demonstrate that stars currently near the bar’s corotation radius can have two distinct origins: (1) inner disc stars that migrated outward via corotation resonance dragging, and (2) stars that formed locally. By applying a simple but physically motivated metallicity enrichment model, we successfully reproduce the observed age–metallicity patterns in the Galactic disc and their dependence on guiding radii. We further explore the implications of this migration mechanism on the chemical cartography of the Milky Way disc, including the [α/Fe]-bimodality and azimuthal metallicity variations. Because this mechanism is closely linked to the pattern speed evolution of the Galactic bar, we are also able to infer the bar's dynamical history: our results suggest that the bar formed approximately 6–8 Gyr ago with an initial pattern speed of 60–100 km/s/kpc, and has since decelerated by 50–70%.

477 Distribution Function-based dynamical modelling of stellar systems

A common task in Galactic dynamics is the inference on the gravitational potential and mass distribution of resolved stellar systems, such as globular clusters, nearby dwarf spheroidal galaxies, or haloes of Andromeda-like galaxies in the local Universe.
In one approach, the tracer population is described by a distribution function (DF) in the space of integrals of motion (e.g. actions), while the gravitational potential may be specified independently or determined by the DF itself. The model parameters are constrained by maximising the likelihood of the observed kinematic dataset, taking into account the incomplete phase-space information (e.g., unknown distance and/or proper motion) as well as measurement uncertainties.
I discuss the strengths and limitations of this technique using several examples:
(1) the Milky Way's nuclear star cluster,
(2) Sculptor dSph,
(3) globular clusters and planetary nebulae in M31.

Speaker: Eugene Vasiliev (University of Surrey)

10:30 Coffee Break

Plenaries 5 - Friday

478 The "carbon footprint" of astronomy and astrophysics

As the impact of the ongoing climate crisis increases, so does our concern about the effect that our activities have on the environment. But what is the "carbon footprint" of our work as astronomers, and what do we need to do to if we want to reach our "net zero" commitments? I will walk you through some of the way our environmental impact is being measured, how bad it is, and what efforts are being done to minimise it.

Speaker: Dr Beatriz Mingo (University of Hertfordshire)

479 Diversity and Inclusion: why they are essential

Ability for science has, can, and always will come from absolutely anywhere. For every form of discrimination - religious, class, gender, ethnic, national, economic, disability, sexuality - one can name scientific geniuses who's ability, insight and contribution could easily have been lost to humanity because of any one of those discriminations. But it goes much deeper than just the potential loss of talent. Decision-making, particularly in emergency and difficult situations, is massively improved if diversity of experience, background and neural pathways are brought to bear and inclusivity is essential to allow that diversity to be able to speak up and contribute. This lesson was learned by NASA, in particular, and missions, and indeed the lives of astronauts, were saved as a result. In the media, the concept of "political correctness gone mad" has evolved into the more aggressive concept of "woke" but starts from the thought that diversity and inclusion are actually unnecessary and driven only by a desire to be nice. In reality, they are indeed the right and humane policies to adopt, but they are far, far more than that, being essential to good decision-making and the harnessing of all human talent. Science has always found itself in conflict with dogma, and progresses by arriving at consensus, and a consensus is only powerful when it is a diverse and inclusive one. We need to be aware of the process by which science arrives at consensus and defend it, for it is under attack by those outside science with vested interests in undermining a scientific consensus.

Speaker: Prof. Mike Lockwood (University of Reading)

12:30 Closing ceremony

12:45 Lunch

Publishing workshop

Organisers: Liz Baker, David Flower, Alice Power, Helen Klus

Getting published – MNRAS author workshop

For all students and early-career researchers looking to publish their research.
The course will be run by the MNRAS Editor-in-Chief and journal staff and will cover:
o Choosing the right journal 
o How to write a good paper
o MNRAS submission process
o How the review process works
o How to respond to referee reports
o Ethical issues associated with research publishing
o Production and online publication

Pathways to sustainable research in astrophysics, cosmology, and instrumentation

Organisers: Nazim Bharmal, Lindsay Stringer, Meryem Kubra Dag

Ensuring that human activities are, or that they can become, environmentally sustainable is essential in order avoid the worst effects of climate change. There is also an imperative for scientists to undertake environmentally responsible research and innovation activities, with research funders increasingly requiring green lab certifications. For an individual researcher in astronomy and adjacent fields, it is not easy to understand what the impact is from their professional activities. Environmental impacts can originate from a large number of disprate sources, from locally within their institute all the way up to the shared use of global facilities such as telescopes and super-computers. This session aims to convene the people who want to take positive action, so that together we can develop our understanding of how research can be effectively carried out while simultaneously minimising its environmental impact. It will consider existing good practices and identify what else we can do to make our science more environmentally sustainable, with a view to informing a wider conversation and set of actions.

How do we make progress in science?

Organisers: David Alexander, Ryan Hickox, Ulrike Kuchner

How do we make progress in scientific (more specifically astronomy) research? Astronomy is strongly driven by new facilities, cutting edge observatories that explore new regions of parameter space and ever more powerful computers that allow for the investigation of more refined physics at higher spatial and temporal resolution. But scientific progress is more than just exploitation of new facilities: larger datasets from existing facilities, the utilisation of new analysis techniques, possibly adapted from different disciplines, facilitated community engagement, and inspiration are also powerful drivers of progress.

In this lunchtime session we, a group of astronomers, philosophers, and sociologists, aim to discuss how scientists make progress in research and how we can recognise and track this progress, including demonstrating some of the tools and approaches at our disposal. All are welcome to join!

Convener: David Alexander (Durham University)

Galaxy formation simulations at the Frontier

Organisers: Sarah Johnston, Stephen Wilkins; co organisers: Sownak Bose, Sophie Koudmani, Andrew Pontzen, Sandro Tachella

For over a decade, cosmological galaxy formation simulations have had a transformative impact on modern extragalactic astronomy, becoming indispensable tools for understanding galaxy formation and evolution. This session examines three major frontiers in galaxy formation modelling:

Observational Frontier: revolutionary data from the James Webb Space Telescope has revealed unexpected phenomena – surprisingly abundant bright ultra-high redshift galaxies, early SMBHs, and early quiescent galaxies, and unique chemical signatures – posing challenges to current models. Observations from Webb will soon be complemented by upcoming wide-area surveys (Rubin/LSST, DESI, 4MOST, Euclid), and future observatories (SKA, ELTs, LISA) will expand the scope of observational constraints with unprecedented area, sensitivity, wavelength coverage, and resolution. Together these will provide new opportunities to test and refine models.

Meeting these observational challenges is the Physics Frontier: models are continuing to increase in complexity, adding processes like radiative transfer, magnetohydrodynamics, and more sophisticated modelling of SMBHs and star formation.

Meeting the challenge of more sophisticated models and large volumes is the Scale Frontier: thanks to improvements in code efficiency and access to new facilities, entering the exascale regime, simulations can increase in complexity, resolution, volume, or number; with large ensembles of simulations now allowing the systematic exploration of model parameters.

This session will focus on results from these three frontiers: the observations that are challenging current models and informing next generation models, the new physics being implemented, and the prospects for the future in the exascale regime.

480 The FLARES view of early AGN

A fundamental question in our understanding of supermassive black holes (SMBHs) is how they formed and how they subsequently impacted their hosts. Significant progress has been made in recent years, driven by remarkable spectral data from JWST, which provides extensive coverage of UV-optical emission lines in the high-redshift Universe (z>5). This provides crucial information about the physical properties of AGN and the ISM surrounding them.

One of the objectives of the First Light And Reionisation Epoch Simulations (FLARES), a novel suite of hydrodynamical cosmological zoom simulations, is to explore these phenomena. The FLARES strategy allows us to simulate much larger effective volumes than possible with traditional periodic box methods, making it ideal to study the formation and evolution of AGN, and its impact on the host galaxy in the distant Universe.

In this talk I will present insights from FLARES, by first exploring predictions for the physical properties of SMBHs, and their hosts. I will also discuss the impact of SMBHs on their hosts using insights gained through matched simulations entirely without AGN feedback, or other modelling changes. Finally, I will introduce a new AGN emission model, combining disc, broad-line regions (BLR), narrow-line region (NLR), and torus components, incorporated into the open-source 'synthesizer' synthetic observations pipeline. When coupled with FLARES or other simulations, this allows us to predict the rest-frame X-ray to far-IR emission, including line emission. This enables us to make direct comparison with observational surveys, avoiding the need for complex and poorly motivated completeness corrections.

Speaker: Aswin Payyoor Vijayan (University of Sussex)

481 Dwarf Galaxy Growth Across the Cosmic Web

Dwarf galaxies are considered laboratories for studying the assembly of galaxies in the early universe, and their properties at final day may vary as a function of environment. In our work, we used the DM-only simulation COCO, along with the semi-analytic model GALFORM to investigate the differences in dwarf stellar mass assembly between different areas of the cosmic web. This allows us to investigate dwarf galaxies in a cosmological environment, which we would be unable to do with hydrodynamic simulations. Our findings show large trends in the stellar mass assemblies of dwarfs, with satellites in nodes assembling an average of 1.78 Gyrs earlier than satellites in walls, but only 0.23 Gyrs earlier for central galaxies. Satellite galaxies show strong dependence of mass assembly on environment, which is driven predominantly by the epoch at which an object becomes part of a larger host in different regions of the cosmic web. On the other hand, central galaxies do not show trends as significant as those of their host dark matter haloes due to the differences in the stellar to halo mass relation between different areas of the cosmic web. We also investigate the effect of varying parameters controlling the timing and filtering scale for reionisation, finding significant effects particularly in the regime of ultrafaints. This work is unique in providing a statistical investigation of the stellar mass assemblies of galaxies in this mass regime, and how those properties depend on the parameters of reionisation.

482 Introducing the Kiara Simulations

I will present the new Kiara galaxy formation simulations. Embedded within the SWIFT cosmological hydrodynamics code, Kiara builds on the successful Simba simulation model to incorporate a number of new physical processes such as a subgrid dust-H2-SF ISM model, non-decoupled kinetic winds, and state of the art chemical evolution. I will also update progress on ongoing work towards Kiara-RT for radiative hydrodynamics simulations of the early Universe. I will describe these models and present initial results, particularly exploring the expanded range of observational comparisons enabled using Kiara's novel input physics.

483 Understanding the role of mergers and assembly history in shaping MW-like galaxies with `genetically modified' simulations: the dependence on subgrid physics

Galaxy mergers play an important role in galaxy evolution. However, whether and how they shape galaxy properties on multi-Gyr timescales is less well understood. Furthermore, the overall assembly history of a galaxy and its host halo is crucial in determining several of its properties and those of its satellite population. Understanding the causal relationships between assembly and merger histories and galaxy and satellite properties from simulations poses two significant challenges: the large stochastic differences between assembly histories that must be simulated, and the inherent uncertainty in the subgrid prescriptions implemented in the codes. To tackle both, we present results from the PARADIGM project, a suite of zoom-in cosmological hydrodynamical simulations of Milky Way (MW)-mass haloes -- using `genetic modifications' of the initial conditions (ICs) with the GenetIC code to generate controlled alterations to a galaxy's assembly history in a systematic way, and using different simulation codes to understand the impact of different subgrid implementations of galaxy formation. By evolving the same ICs with the VINTERGATAN and IllustrisTNG galaxy formation models, we explore how the overall assembly history impacts the $z=0$ properties of the central galaxy and its satellite populations. We show that the size and kinematics of the central galaxy respond similarly to the altered merger histories in the two codes, with larger mergers resulting in smaller, more spheroidal galaxies. We also consider the response of satellite destruction timescales and the star-formation histories of surviving satellites, finding similar distributions of disruption timescales and quenching times between the two codes.

484 Unveiling the kinematics of galaxies during the Epoch of Reionisation with the THESAN-Zoom simulations

In its first few years of operation, the James Webb Space Telescope (JWST) has revolutionised our understanding of galaxy formation in the early Universe. For the first time, its unprecedented sensitivity and spatial resolution have enabled direct constraints on the kinematics of ionised gas during the Epoch of Reionisation. Through NIRSpec IFU and MOS observations, along with NIRCam WFSS data, JWST has provided detailed measurements of the ionised gas dynamics, offering new insights into the internal motions of high-redshift galaxies. These observations, when combined with state-of-the-art cosmological simulations, are allowing the extragalactic astronomy community to make significant advances in characterising the first generation of galaxies and testing the current cosmological framework.

To interpret these observations, we use the THESAN-zoom simulations—a suite of high-resolution, zoom-in radiation-hydrodynamic simulations. These simulations preserve the realistic reionisation history of the parent simulation while incorporating updated stellar feedback and multi-phase interstellar medium physics, making them an ideal theoretical counterpart to JWST’s observational efforts. By analysing the kinematics of stars, dark matter, and gas (across cold, warm, and hot phases), as well as the H-alpha emitting ionised gas, we examine key properties such as rotational velocity, velocity dispersion, circularity, and spin. This comprehensive kinematic analysis provides new constraints on the rotational support and feedback processes in early galaxies, which are critical for estimating their stellar masses and understanding their dynamical evolution during the Epoch of Reionisation.

485 Atomic gas in galaxies in the Colibre simulations

I will present first results from the new Colibre simulations with a focus on atomic gas in galaxies. These simulations build on the successes of the EAGLE project with comprehensive changes to the treatment of cold gas in particular. Whereas many contemporary simulations impose a gas temperature floor around 10^4 K, in Colibre gas cools to ~10 K. Atomic and molecular hydrogen is modelled self-consistently via a state-of-the-art chemical network implementation including non-equilibrium effects for a subset of reactions including HI-H2. The model's predictions for HI properties of galaxies are remarkably well-converged with numerical resolution and only minimal resolution-dependent adjustments of model parameters. Early comparisons with the observed HI mass function, stellar mass - HI fraction relation, HI mass-size relation, HI velocity width function and other scaling relations offer encouragement that these simulations will be an excellent tool to interpret surveys of HI in galaxies.

The UK White Dwarf Community: An Opportunity to Connect

Organisers: Andy Buchan, Emily Roberts, Jamie Williams

Although the field of white dwarf research in the UK is rapidly expanding, meetings focused on this subject remain infrequent. Following the success of the white dwarf session at NAM 2022, we propose another session in 2025 to allow the presentation of new work, particularly by early career researchers. There have been many new developments in the field since the last NAM session. These include data releases from JWST and DESI, as well as the application of machine learning techniques to white dwarf spectra. With the primary white dwarf meeting, EuroWD, only occurring biennially and the next conference being held in Boston, there are few opportunities for early career researchers in the UK to present their work and for collaborations to begin and be fostered. As the previous white dwarf session envisioned, we propose white dwarf NAM meetings in the off-years from EuroWD, in order to grant more chances for the community to meet. We invite talks on any topic related to white dwarfs including, but not limited to, stellar archaeology, evolved planetary systems, white dwarf modelling, and supernovae. These topics will not only help progress our understanding of white dwarfs, but will have wide-ranging impacts on other areas of astronomy, including planet formation, galactic evolution and transients. We will give priority to early career researchers, allowing them an opportunity to present their work and develop collaborations with the wider community.

14:15 Prep time

486 Characterisation of a white dwarf with transiting debris in the habitable zone

The recent discoveries of transits around white dwarfs have provided unique and powerful insights into their circumstellar debris discs. This family of white dwarfs with transiting debris exhibits significant diversity, where some display line-of-sight gas absorption while others are highly dynamic with large scale heights.

In 2022, a white dwarf was reported to have transiting debris at an orbital period of 25h, which places its circumstellar material in the habitable zone, where a planetary surface can support liquid water. The light curves show myriad unusual features, with the most pronounced dimming components every 23 min – the 65th harmonic of the fundamental period – and numerous orbital drifters.

I will present time-resolved X-Shooter spectroscopic data of WD1054–226, which demonstrate significant spectroscopic variability, a hallmark of circumstellar gas along the line of sight. Our team has also obtained ultraviolet spectra with Hubble, which will crucially allow us to differentiate between volatile and refractory compositions of the parent body, and near-infrared light curves from HAWK-I, which enable investigations into the colour dependence, and therefore the size distribution, of the transiting material. Finally, an update will be provided on the long-term stability of the 65th harmonic and the presence of the drifting components over a timescale of four years, facilitated by new multi-band light curves from ULTRACAM.

487 Uncovering hidden white dwarf binary populations using Gaia and Galex

White dwarfs with a F, G or K type companion represent the last common ancestor for a plethora of exotic systems throughout the galaxy, though to this point few of them have been fully characterised in terms of orbital period and component masses, despite the fact several thousand have been identified. Gaia DR3 has examined many hundreds of thousands of binary systems, and as such we can use this, in conjunction with previous UV excess catalogues, to perform SED fitting in order to obtain a sample of 206 binaries likely to contain a white dwarf, complete with orbital periods, and either a direct measurement of the component masses for astrometric systems, or a lower limit on the component masses for spectroscopic systems. Of this sample of 206, four have previously been observed with HST spectroscopically in the ultraviolet, which has confirmed the presence of a white dwarf, and we find excellent agreement between the dynamical and spectroscopic masses of the white dwarfs in these systems. In this talk, I will present our findings; that white dwarf plus F, G or K binaries can have a wide range of orbital periods, from less than a day to many hundreds of days. A large number of our systems are likely post-stable mass transfer systems based on their mass/period relationships, while others are difficult to explain either via stable mass transfer or standard common envelope evolution. I will also present preliminary results of expanding this search to a much larger sample.

Speaker: James Garbutt (University of Sheffield)

488 A different perspective: how the choice of disc model affects the interpretation of polluted white dwarfs

At least a quarter of white dwarfs display signatures of atmospheric pollution of heavy metals in their spectra, caused by the accretion of planetary debris. This debris is thought to originate from planetesimals that are tidally disrupted, forming a debris disc. The material in the disc is then accreted onto the white dwarf, generating the pollution we observe. I will discuss how this accretion process is commonly modelled and whether a different choice of model, one in which the accretion rate decays exponentially, affects the interpretation of the composition of the material. I will show how our analysis of two cool, helium-atmosphere polluted white dwarfs depends on the choice of disc model, demonstrating the phases of accretion that a simplified disc model would miss. With our analysis, both white dwarfs were found to be accreting rocky planetary material with a bulk composition similar to that of the Earth, and the total amount of accreted material for each star ranged from a small moon to dwarf planet in mass. These two white dwarfs, though typical in their polluted material composition, provide an ideal starting point to test disc models, due to their low temperatures and long sinking timescales.

489 White dwarfs in DESI DR1

The first data release from the Dark Energy Spectroscopic Instrument has yielded the largest sample of spectroscopically-confirmed white dwarfs, observed in an almost-unbiased, magnitude-limited survey. Our catalogue contains over 40000 white dwarfs, around two-thirds of which are newly-identified, all with spectral classifications and stellar parameters from model-fitting. Highlights include many new planetary systems and interacting binaries, plus some rare and exotic objects. I will give a brief tour through the catalogue, and reflect on whether human spectral classification still has a place in the machine-learning era.

490 Overly Luminous Type Ia Supernovae from Super-Chandrasekhar Mass Highly Magnetised White Dwarfs

We observe in nature overly luminous Type Ia supernovae which, if we take to have originated from the deflagration of a CO white dwarf, would imply a progenitor with a mass in excess of the Chandrasekhar mass. There are a number of possible mechanisms by which such a super-Chandrasekhar mass white dwarf may be supported. We consider the presence of a large (>10⁶ G) magnetic field in the white dwarf, the magnetic pressure from which provides necessary support to allow WDs to exist far above the Chandrasekhar mass, which we call "Highly magnetised white dwarfs", or B-WDs. To conduct simulations as part of Bhattacharya et al. (2021), we developed a heavily modified version of the STARS stellar evolution code (Eggleton (1971) and many updates since), incorporating prescriptions of Gupta et al. (2020) and Mukhopadhyay et al. (2021) to compute magnetic field strength at each calculation point in a WD model, along with the magnetic contributions to pressure and density.
We consider the possibility that this magnetic field support prescription can provide a mechanism to actually detonate super Chandrasekhar mass white dwarfs, and hence to produce overly luminous Type Ia supernovae. If we consider the decay of this magnetic field owing to Ohmic decay and Hall Drift, we obtain a possible trigger for the detonation. For various values of white dwarf mass and initial magnetic field strength this allows a range of supernova luminosities above those expected from single degenerate Chandrasekhar mass WD detonations to be achieved from this mechanism alone.

Speaker: Alexander Hackett (CEICO - FZÚ-AVČR - The Physical Institute of the Czech Academy of Sciences & Institute of Astronomy, University of Cambridge, Cambridge, UK)

491 The discovery of new eclipsing white dwarf binary systems from NGTS

The vast majority of stars -- $\sim$95\% -- are born with masses below 8-10 M$_{\odot}$ and will eventually evolve into a white dwarf. Because of this, white dwarfs play an integral role in deepening our understanding of the structure and evolutionary history of stellar bodies. They, however, present observational limitations because of their Earth-like radius and low luminosity. Since about a third of all white dwarfs are in binary systems, many of them in very close ($\sim$hours) orbits, transit events have been highlighted as a key method to help discover these systems. In this talk, I will discuss my search for eclipsing binary systems containing a white dwarf, which was conducted using the Next Generation Transit Survey (NGTS) private data archive. I will showcase the capabilities of NGTS in capturing such events from newly discovered candidates and present preliminary analysis through the use of methods such as Box-least squares and Lomb-Scargle algorithms and Spectral Energy Distribution fitting. With my analysis, I am able to obtain preliminary model-dependent orbital and physical parameters for the candidates, from which inferences can be made about the potential evolutionary history of the binary system. These results highlight the potential of NGTS to study faint binary systems, which allows us to conduct a blind survey of areas of the sky to discover new and important systems.

492 Investigating the origin of the lowest-mass white dwarf stars

ELMs are white dwarf stars with masses that are too low ($\lesssim$ 0.3 $M_\odot$) to be formed through single stellar evolution. Many of the observed ELMs have been found to be strong gravitational wave sources that will be detectable by LISA. Their higher brightness compared to canonical white dwarfs makes them valuable laboratories for the development of multi-messenger astronomy. Binary interaction seems to play an important role in the formation of ELMs since it can cause the mass-loss required to explain their masses. This raises important questions: Do all low-mass white dwarfs result from binary evolution, or can other evolutionary paths exist? Does the companion always survive the interaction, or can it be destroyed, leaving behind a single low-mass white dwarf?

My PhD research aims to get new insights about these questions, as will be shown in this talk. To achieve this, I have selected a complete volume-limited sample of ELM candidates from the Gaia DR2 ELM candidates catalogue.
By cross-matching this sample with archives of spectroscopic data (such as SOAR, ESO, INT, LAMOST), I have obtained spectra for 75% of the targets. To complete the sample, I plan to obtain follow-up spectroscopy for the remaining 25% of candidates.
The spectral analysis will allow me to characterize the candidates by fitting parameters such as effective temperature and surface gravity, as well as study ELMs binary fraction by estimating radial velocities.

493 Long term spectral monitoring of a small sample of white dwarfs

We present high resolution archive spectra of four white dwarfs taken over a period of 25 years. The observations were taken with ESOs Ultraviolet and Visual Echelle Spectrograph (UVES) and there are between 400 and 625 spectra per wavelength setting per star. The primary aims of the study are to search for changes in interstellar lines and those in the Earth's atmosphere as a function of epoch, but the same observations may also be used to search for metal lines in the WDs and their possible variation.

Ins and Outs of Accretion: The Consequences of Mass Transfer onto Compact Objects

Organisers: Noel Castro Segura, Melissa Ewing, Scott Hagen, Amy Knight, Martina Veresvarska, Federico Vincentelli

Accretion processes are ubiquitous throughout the universe and play a crucial role in the evolution of astrophysical systems across all size scales. Accretion often occurs in binary systems like white dwarfs and X-ray binaries, which can host neutron stars or stellar mass black holes. Here, the gravitational pull of a compact object draws material from its companion star, resulting in bright emission across the electromagnetic spectrum. The consequences of accretion in binaries are widespread and vital when investigating supernovae progenitors, energetic transients and gravitational regimes. Despite the diversity among accreting systems, accretion itself is scale-invariant. Therefore, gathering the accretion community at NAM is essential to foster discussions of the connections and analogies between different classes of accreting systems and the advancements from forthcoming missions like NewAthena.

In this session, we will discuss the inward and outward flow of mass, energy and angular momentum in white dwarf, neutron star and black hole binaries and their consequences, covering topics from accretion disc radiation and outflows to thermonuclear bursts and quasi-periodic oscillations. Historically, high-energy astrophysics sessions at NAM have combined discussions of accreting binaries with supermassive black holes.

14:15 Prep time

494 A New Pulsating Ultraluminous X-ray Source Candidate in Centaurus A

The discovery of coherent X-ray pulsations from ultraluminous X-ray sources (ULXs) provided the first concrete evidence that some ULXs host neutron stars (NSs) accreting at super-Eddington rates.  This raises many new questions regarding the physics of super-Eddington accretion in the presence of strong magnetic fields and the fraction of the ULX population hosting NS accretors. One way to address these questions is to find more ULXs harbouring NSs, thereby increasing the population of known NS ULXs and enabling improved characterisation.  In this talk, I report the discovery of a new candidate pulsating ultraluminous X-ray source (PULX) in NGC 5128 (Centaurus A). The candidate, 4XMM J132542.2–425943, is a known ULX and exhibits coherent pulsations at a frequency of 1.269 Hz in a single XMM-Newton observation at marginal significance. Unusually, the candidate displays a softer X-ray spectrum than other known PULXs. Identifying this candidate required a new approach to pulsation searches that accounts for the intrinsic randomisation employed during data reduction, which can introduce significant uncertainties in the strength of pulsation detections, potentially resulting in viable PULX candidates being unnecessarily discarded or vice versa. I will discuss this new search approach within the context of verifying the marginal signal from 4XMM J132542.2–425943 and how this approach can assist in expanding the population of NS ULXs.

Speaker: Amy Knight (Durham University)

495 Distinguishing between Accretion Precession Models in NGC5907 ULX with Phase Coherence Analysis

Ultraluminous X-ray sources challenge our understanding of extreme accretion regimes, particularly ULX pulsars like NGC5907 ULX1. This remarkable system exceeds the neutron star Eddington limit by a factor of ~500 (L_X,peak ~10^41 erg/s) and exhibits a ~78-day super-orbital periodicity, providing a test case - as the most luminous ULX pulsar - to differentiate between competing descriptions of super-Eddington accretion.

We present results from Swift XRT monitoring data (2020-2023) that confirm the persistence of the ~78-day modulation in the latest high-flux observational epoch. An extended low-flux off-state separates the recent 2020-2023 high-flux activity from the 2014-2016 high-flux epoch, providing a crucial opportunity to explore phase coherence between these distinct observational epochs. Since the magnetic precession scenario allows for total phase coherence, whereas the Lense-Thirring precession model predicts a likely phase discontinuity following a significant change in accretion rate, we explore using the measurement of phase coherence as a test to determine the driving mechanism for the super-orbital modulation in NGC5907 ULX1.

Distinguishing between models for the origin of super-orbital modulation may provide independent constraints on the magnetic field strength of the ULX pulsar. The neutron star's magnetic field introduces additional structure that influences both the overall spectral characteristics as well as the long-term periodic behaviour. Our study of NGC5907 ULX1 contributes to the ongoing discussion on the role of the magnetic field in producing the extreme luminosities observed in the ULX population.

Speaker: Nabil Brice (University of Hertfordshire)

496 The very high X-ray polarisation of accreting black hole IGRJ17091-3624 in the hard state

The Imaging X-ray Polarimetry Explorer (IXPE) provides, for the first time, sensitivity to X-ray polarisation in the 2–8 keV band, offering two powerful diagnostics to probe the extreme physics of accreting matter around compact objects: polarisation degree (PD) and polarisation angle (PA). I will present results from the first IXPE observation of the black hole X-ray binary (BH-XRB) IGR J17091, a system renowned for its extraordinary variability, including ‘heartbeat’-like oscillations. Our spectro-polarimetric and model-independent analyses reveal an unexpectedly high PD of 9.1 ± 1.6% at a PA of 83° ± 5°— the highest ever measured for a BH-XRB in the corona-dominated hard state. I will discuss these results alongside our energy-resolved polarimetric analysis, which hints at a positive correlation between PD and energy, as well as the influence of the source’s structured variability on the polarisation properties. I will then explore potential models to explain this extreme PD, including simulations investigating the role of polarised disc winds and relativistic coronal outflows.

497 Are jets from stellar mass black holes as fast as those from supermassive black holes?

Jets from stellar mass black holes in X-ray binaries (XRBs) and supermassive black holes in blazars provide distinct opportunities to study the jets of black holes across two different mass regimes. They also represent samples with very different selection effects. Historically, the apparent speeds of XRB jets have been observed to be lower than those of blazars, leading to the assumption that this reflects the underlying distributions of Lorentz factors, i.e. stellar mass black holes produce slower jets. In this talk, I will present our detailed modelling of the parent population for large-scale XRB jets, which accounts for the selection effects present in the observed sample. Using nested sampling, we determined that the Lorentz factors of the parent population of XRBs are best described by a power law with a slope of $b = 3.01_{-1.23}^{+0.89}$, the same form of model which has been historically applied to blazar jets. We can reject several other potential Lorentz factor distributions, such as Gaussian and Exponential distributions, using Bayes factors. When comparing our findings to the parent Lorentz distributions of Blazar jets documented in the literature, it is notable that we cannot rule out the possibility that both XRBs and Blazar jets share the same parent population Lorentz factor distribution. In other words, based on kinematics alone, jets from stellar mass black holes are consistent with being just as relativistic as those from supermassive black holes.

498 Spectral-Timing Analysis of Swift J1727.8-1613 Using Insigh-HXMT Observations

We present a comprehensive spectral and timing analysis of the newly discovered black hole transient Swift J1727.8-1613, based on broadband (1-150 keV) observations from Insight-HXMT during its 2023 outburst. Using the flexible, energy-conserving SSsed model, we identify the presence of both thermal and non-thermal Comptonization components in the hard component dominated state. We track the evolution of the truncated accretion disc radius, $R_{\rm tr}$, which decreases from 45 $R_{\rm g}$ to 9 $R_{\rm g}$, consistent with the transition from the hard to the intermediate state. Additionally, we explore the correlation between $R_{\rm cor}$ and the centroid frequency of quasi-periodic oscillations (QPOs; $\nu_{\rm c}$) to test the hot flow Lense-Thirring (LT) precession model. The overall trend is consistent with LT precession predictions, showing a decrease in the scale height-to-radius ratio ($h/r$) as the source evolves. However, deviations in the $R_{\rm cor}$-$\nu_{\rm c}$ relation imply additional contributing factors, such as escaped jet power, flipped inner disc, and variations in the hot flow height.

499 The changing face of UV emission: Tracing MAXI J1820+070 across a state transition

In this talk, I will present Hubble Space Telescope (HST) and AstroSat ultraviolet (UV) spectroscopy of the black hole X-ray binary MAXI J1820+070 during its 2018 outburst. Our observations span three accretion states—luminous hard, hard-intermediate, and soft state—providing a rare multi-state UV view of this system. The source exhibits remarkably low extinction, E(B-V) = 0.2 ± 0.05, making it an exceptional laboratory for studying UV emission in LMXBs. It displays surprisingly similar spectra across states, challenging standard irradiated disc models. I will discuss how all UV emission lines are double-peaked, with higher-ionisation lines (e.g., N V, C IV) showing broader profiles than lower-ionisation transitions—a clear signature of their accretion disc origin. Notably, no blue-shifted absorption features are detected, despite previous reports of outflows in optical/NIR during the hard state. I will also highlight how line ratios point to near-solar abundances, supporting a low-mass companion. Finally, I will present our time-resolved HST analysis, revealing a broken power-law variability spectrum and a tentative ~18s quasi-periodic oscillation (QPO)—consistent with signals seen in other bands. These results suggest that UV emission in LMXBs is more complex than simple reprocessing, potentially involving additional physical processes.

This talk will emphasise why MAXI J1820+070 is a benchmark system for UV studies of accretion and how our findings motivate future multi-wavelength campaigns to unravel the underlying physics.

500 The Quiet Majority: Photometric Signatures of Non-Accreting Compact Objects in Luminous Binaries

Current estimates suggest that the Milky Way contains approximately 100 million stellar-mass black holes; however, only about 100 have been detected, mainly due to the bright X-ray signal resulting from rapid accretion events from a close binary partner. The population of black holes in wide, non-accreting binaries with a companion star, predicted to be around 10 million, remains elusive, with only a handful identified through astrometry and radial velocity techniques. I will present a novel methodological framework for detecting these quiet black holes through photometric gravitational lensing signatures in binary systems. Our approach builds on exoplanet transit detection methods, with the transit causing a lensing flare in place of a dip. We incorporate eccentric orbital dynamics leading to viewpoint-dependent variations in the Einstein radius, and self-consistent stellar limb darkening law, enabling multi-wavelength analyses. Initial simulations of plausible eccentric systems reveal characteristic asymmetric flux amplification of 0.1% to 2%, which should be detectable in high-cadence surveys such as TESS and ZTF. While these lensing signals are transient and sensitive to viewing geometry, our analysis indicates that high-inclination systems with periodic signatures and well-constrained orbital parameters could be identified through phase-resolved analysis. I will discuss how we may adapt existing exoplanet transit search pipelines for lensing detection and expectations for future detections.

501 Phased accretion and a dynamically-truncated eccentric circumbinary disc cavity in a pre-main-sequence binary system

Pre-main-sequence binary systems provide a unique laboratory for studying dynamical truncation in discs. We studied the inner region of a nearby Herbig Ae/Be binary system using the VLTI/GRAVITY and VLTI/PIONIER instrument. Spectrally-dispersed interferometry with GRAVITY allowed us to determine the origin of the Br γ line emission and to study how the accretion rates on the primary and secondary vary over the orbit.

We constrained the orbit and dynamical masses of the stars, and resolved dust arranged in a circumbinary disc. The measured inner disc radius is considerably larger than the theoretical dust sublimation radius, suggesting that the disc is dynamical truncated by the binary. One side of the circumbinary disc appears consistently brighter, indicating that the disc cavity is eccentric, which matches the prediction from smooth-particle hydrodynamic simulations of eccentric binaries. Finally, we found that the variable Br γ line emission is associated with accretion onto the primary and secondary. We derived the individual accretion rates and found that the primary accretes at roughly constant rate, while the accretion rate on the secondary is strongly phase-dependent and peaks around periastron passage.

Jobs in Astronomy and Geophysics

Organisers: RAS Early-Career Network, Matthew Temple, Marieta Valdivia Lefort

The RAS Early-Career Network Steering Group will organise a skills session featuring 3-4 talks aimed at students and early-career researchers who are considering careers in astronomy and geophysics. The presentations will cover topics such as how to find and apply for postdoc positions, how to apply for fellowships (in the UK and abroad), and how to best prepare for academic job interviews.

There will also be time for attendees to ask general questions to the speakers in a panel discussion format.

This careers panel is organised by the Early Career Network (ECN) of the RAS. We do not seek abstract submissions for this session but you are welcome to get in touch with the ECN with recommendations for panellists.

502 Finding and applying for jobs

Speaker: Beatriz Mingo (University of Hertfordshire)

503 Writing Research Proposals

Speaker: Francesca Fragkoudi (Durham University)

504 Postdoc Interviews

Speaker: Sownak Bose (Durham University)

15:15 Panel discussion / Q&A

Spacecraft Disposal by Impact on the Lunar Surface: The Next Big Threat to Astronomy and Planetary Science?

Organiser: John Zarnecki; co organiser: Julie Holt-Jones, Fionagh Thomson

Over the next decade, there seems little doubt that we will see a burgeoning lunar ‘economy’, involving science, exploration and commerce. Estimates suggest some 150 such launches in the next 10 years. Many of these spacecraft will be placed into lunar orbit to provide communications, navigation and monitoring capabilities for lunar-based facilities. There are limited end-of-life options for spacecrafts orbiting the Moon, unlike the Earth where there are designated graveyard orbits to move up or down into, oceans to land in and an atmosphere to burn up in on re-entry. Therefore, it appears highly likely that in the short- to medium-term, lunar-orbiting spacecraft will be disposed of through impact onto the lunar surface. This type of post mission disposal offers significant technical, environmental and ethical challenges to the future of astronomy and planetary science activities on the moon. Consequently, the unintended consequences could be disastrous, if not regulated or/and mitigated in an effective way.

This session will address this impending challenge to Science and will ask:
o What might be done to mitigate any potential negative unintended consequences?
o What could we learn from current discussions and research on disposal options for Earth’s orbits, if any?

Timetable_#84.csv

14:15 Welcome remarks

505 Modelling spacecraft disposal onto the lunar surface

Intentionally crashing spacecraft onto the lunar surface poses a potential hazard to human life and infrastructure on the Moon, but also presents an opportunity for scientific discovery. Spacecraft impacts would eject rocks and dust across the Moon at high speed. Without deceleration by an atmosphere, these high speed particles would pose a hazard to habitation and infrastructure. The large speeds of impacting spacecraft mean that this situation is best addressed using computer simulations. While our incomplete knowledge of the target properties creates uncertainty for such models, it also provides an opportunity to learn about the lunar subsurface.

We will describe our state-of-the-art simulation capabilities and how they could be deployed to quantify the pollution caused by such events. This would include predictions of the mass of ejecta, the distribution of ejection speeds and directions, and the extent of the seismic shaking caused by the impact itself.

In 2009, NASA's LCROSS mission ended with a deliberate 2.5km/s impact into the permanently shaded Cabeus crater near to the lunar south pole, as part of the quest for subsurface water ice. We can adapt our numerical models to use targets with different compositions and physical properties. In this way, one may be able to learn about the porosity and thickness of the lunar regolith or even the presence of subsurface volatiles.

Speaker: Dr Vincent Eke (Durham University)

506 SMART-1 end of life: lessons learnt from a lunar impact ending

The ESA SMART-1 spacecraft reached its end of life (EOL) in Sept. 2006, when it was deliberately crashed into the Moon at 2 km/s [1-5]. ESA chose this EOL strategy as a reasonable way to end the mission and remove the spacecraft from the environment. Given that cis-lunar space will be increasingly populated with spacecraft (and associated upper stages etc.), it can be assumed that more EOL events will be required to avoid polluting that space. The demise of SMART-1 will be discussed, as an aid to understanding what happens in an EOL event where the spacecraft impacts the Moon. Not only is a crater formed, but an impact light flash occurs, a dust plume rises, and ejecta is throw away from the impact site. Indeed, if the impact is at a shallow angle (as was the case with SMART-1, where it was approx. 2°) the spacecraft can ricochet away from the primary impact point. Based on the experience of SMART-1, lessons will be suggested and opportunities and threats identified.

[1] Veillet C. and Foing B. 2007. 38th Lunar and Planetary Science Conf., abstract #1520. [2] Ehrenfreund P., et al. 2007. 38th Lunar and Planetary Science Conf., abstract 2446. [3] Burchell M.J., et al. 2010. Icarus 207, 28-38 [4] Burchell M.J., et al. 2015. MAPS 50, 1436 – 1448. [5] Stooke, P.J. 2019. Icarus 321, 112-115.

14:55 Missing invited talk*

507 Regulating lunar-based activities without rigorous evidence: the case of disposing of spacecrafts on the moon’s surface at their end of their working life

Implementing new regulations into the existing everyday practices of different stakeholders is often challenging. One pragmatic approach is to build on reliable and rigorous evidence to help guide the process. But not everything in space is well understood and implementing regulations with limited underlying evidence can lead to disputes. One imminent example is the (unknown) impact of disposing of spacecrafts on the moon’s surface at their end of their working life. Should we wait until we have reliable scientific evidence - that could take years - or until negative (unforeseen) impacts are observed, when it may be too late to reverse any damage. 

We discuss the wider ethics and potential trade-offs between space exploration and astronomy/planetary science. Drawing on current discussions of disposal options for spacecrafts re-entering Earth’s atmosphere - we ask:
* How do we effectively implement regulations in this type of scenario - and can/should we?

15:15 Panel

15:35 Q&As

15:44 Closing comments

Crossing Boundaries: The benefits of ArtScience for contemporary astronomy research

Organisers: Ulrike Kuchner, Soheb Mandhai; co organisers: Jenni French, John Paice, Jake Noel-Storr, Houda Haidar

Art and science both expand human knowledge by blending imaginative thinking with analytical decision-making to create original ideas. Despite their historical synergy, fully harnessing their potential in today’s astronomy research is challenging. Ever-growing data, large-scale collaborations, and the rise of artificial intelligence often limit opportunities for creative engagement with complex ideas and data. Artistic methods like virtual reality, music, digital and performance art, offer inclusive ways for exploration, understanding and communication.

While art is widely used for information visualization in outreach and science communication, this session focuses on three less-explored aspects of ArtScience:

o Creativity: ArtScience to contribute to knowledge creation will provide an overview of research and practice into ArtScience for interdisciplinary goals (eg. Kuchner+2023; Birsel+2023).
o Inclusivity: ArtScience to improve research culture and accessibility will highlight artistic methods and tools promoting equality, inclusivity, and diversity (eg. Sensory science clubs for neurodiverse audiences).
o STEAM: ArtScience to support teaching and learning will share STEAM (STEM+Art) practice for education (eg. Aguilera+2024).

We will address key challenges, such as navigating differing disciplinary practices, finding funding, and contextualizing collaborative outcomes. Practical advice will include available UK funding schemes, joining communities, setting shared goals, and evaluating results.

508 From Glass to Galaxies: Entangled Visions - How Art Shapes Our Understanding of the Universe

Art is often seen as useful for science communication, visualising concepts for public engagement. This view underestimates significant epistemic contributions of art to scientific knowledge. Art challenges disciplinary assumptions, introduces alternative methodologies, and fosters novel ways of engaging with material phenomena.
This talk explores how art-science collaborations advance scientific research through artistic processes and motivations. Examples are presented where art has directly contributed to breakthroughs across fields, from astrophysics to material science.
Drawing on new materialist perspectives from Bennett, Barad, and Nail, I argue that art-science encounters are inherently valuable, even when their outcomes are unpredictable or not immediately measurable. Nail’s concept of "indeterminate relational processes" resonates with Bennett’s material agency and Barad’s "intra-action," emphasising the entanglement of subject and observer. Collaborations, shaped by both material and conceptual entanglements, push knowledge production beyond traditional disciplinary frameworks.
I compare digital and material encounters, drawing on my experience as both a digital visual effects and a glassblowing artist. While digital technologies like VR provide intuitive understandings, material engagement utilises natural perception and fosters emergent discoveries. This parallels the contrast between simulations and analogue experiments, where unpredictable physical processes reveal the unexpected.
I draw connections between my own work with caustics - structural geometries created by light and glass - and the formation of the cosmic web. Caustic catastrophe singularities form the large-scale structure of the universe, where galaxies and dark matter cluster in a caustic skeleton. This analogy reveals how art can illuminate the fundamental networks and interconnectedness that shape the cosmos.

509 Sounds of Space Project: An Art-Science Collaboration

Sound waves cannot travel in the near perfect vacuum of space, but electromagnetic and gravitational waves can. Converting these waves to sound reveals a series of weird and wonderful noises, known as the ‘sounds of space’, and it's a bit like entering the film set of a 1960’s sci-fi movie! In 2017 we set up an art-science collaboration to find novel ways of exploiting these fascinating ‘sounds’ and sharing them with wider audiences. In this presentation I will introduce a variety of space ‘sounds’ from Earth to beyond the galaxy. I will then describe how we have used them in performances that fuse art and science, music, short films, and in the production of a series of albums. Finally, I will describe how the ‘sounds’ of the Earth’s natural radio emissions have been used to enhance the exploration gameplay in the space simulation video game Elite Dangerous.

510 Exoplanets in Science Fiction

Science fiction (SF) is a genre influenced by science which, in turn, influences science. Astronomers discovered the first exoplanets in the 1990s, but exoplanets featured in SF long before then. This talk presents two studies regarding exoplanets in SF. In the first study, a database of 212 SF exoplanets was analysed using a Bayesian network to find interconnected interactions between planetary characterisation features and literary data. Results reveal SF exoplanets designed after the discovery of real exoplanets are less Earth-like, providing statistical evidence that SF incorporates rapidly-evolving science. In the second study, questionnaire data was collected and analysed from participants in a project to create short SF stories in teams of one scientist and one writer. Results show scientific concerns were incorporated into the story creation decision-making process, and suggest an inspirational role for SF towards its readership’s interest in science. Through the use of quantitative and qualitative methodologies, I investigate SF's portrayal of exoplanet science, which is crucial for understanding the genre’s potential use in science communication.

511 An Early Universe

An Early Universe is an artwork made in collaboration with the Gravity Laboratory at the University of Nottingham. For the last year artist Alistair McClymont has been working alongside scientists taking an active part in the experimental process to investigate the early universe using analogue systems. The creation of the artwork and the experimental scientific process were intimately connected, the science affected the art and in return the art affected the science. An Early Universe offers a glimpse into the first moments after the Big Bang, recreating the extreme dynamics when waves and oscillations shaped the cosmos. The rippling water at the heart of the installation serves as an analogue for the early universe, drawing on the shared mathematical principles that govern both the water’s surface and the early cosmos.

512 THE FINAL FUTURE: A study of human impact on near-Earth and terrestrial environments, considering our complex future on Earth and elsewhere.

My practice-led research takes a detailed look at humans’ dominant environmental footprint in space which mirrors our technologically mediated exploration and transformation of environments on Earth. In an inter-disciplinary weaving of contemporary Fine Art practices, with methodologies employed by space, scientific and environmental domains, the work creatively explores the significance of our present actions, as well as the legacy we leave behind.

 Significant human environmental impact on outer space has increased as the quest to find ‘second life’ has accelerated. In 2021, Perseverance landed on Mars. The previous year, superpowers China and the US began the lunar gold-rush. NASA has a separate program to hire private companies (SpaceX) to fly science experiments and cargo to the Moon ahead of a human landing. In May 2020, NASA unveiled the Artemis Accords which outline policies that will govern mining celestial bodies, similar to those that currently exist for the world's oceans.

The art installation I am researching and planning to build in the grounds of UCL’s Mullard Space Science Laboratory (MSSL), will address these issues in an original exploration of the potential consequences of broadcasting signals across space. Using two radio-faxes, MSSL’s large ground station antenna and nearby greenhouse, I will receive and present live environmental visual and sonic data broadcast over HAM radio frequencies. This investigation of Earth’s technological emissions raises many questions, such as, to what degree do deliberate and unintentional outer space activities, such as transmitting radio messages across the galaxy, provide benefits or harms to Earth and humanity?

513 Space for Everyone - Communicating Space Science Creatively

For more than 15 years, I have had the joy of designing and delivering activities for the National Space Academy and other partners to engage young people and their families with space science. To date projects I have worked on have reached millions of people in the UK and beyond and I would relish the opportunity to discuss what, in my experience, makes combining STEM with the arts so successful and why a broad approach to getting buy-in into space is so vital to Space and Astronomy. Projects I would love to discuss include:

Outreach at festivals, including the Universal Orchestra (recreating the Big Bang through simple music)
Working on a suite of activities to accompany an immersive play around space junk, incorporating drama and STEM
Students exploring and explaining space topics to the public through the production of vlogs
Combining music, dance and space within SEN learning
Collaborating with artists to produce engaging, visually stunning children's space books (I have worked with Dorling Kindersley on multiple space books, authoring 2 myself so far)

I would also like to discuss the challenges we face in engagement today - dwindling attention spans, information overload and discuss how taking a more creative approach, and allowing those we are engaging with to explore space and science through other artistic outlets can combat this, to bring meaningful interactions with lasting impact.

514 The rise of STEAM

Combining science and the arts is becoming commonplace in primary schools, with STEAM clubs appearing around the country. But how common is it for students to study a combination of STEM and arts subjects once they’re given the choice?
After age 16, when students in England can take a range of A-level and other qualifications, neither STEM nor the arts are compulsory. In this session, we’ll start with a look at the relative popularity of these subjects: a controversial topic for some, who argue that changes to school accountability measures and qualification reform in the 2010s are behind a decline in entries to arts subjects.
But does there have to be a choice between STEM and the arts? Not for students who study both areas, with combinations such as art, maths and physics at A-Level among the most popular options. We’ll look at trends in entries to STEAM subject combinations over the last few years, exploring the most common subject combinations, academic and technical or vocational pathways, and the impact of the pandemic.

515 Incorporating arts in astronomy research and outreach at the International Astronomical Youth Camp

The International Astronomical Youth Camp (IAYC) is a unique 3 week research camp for 16 to 24 year olds which has brought astronomy and culture together for over 50 years. Each year, as part of our project offerings (alongside traditional observation, theory, and coding project groups), we create groups which intersect astronomy with the arts, humanities, and social sciences. These interdisciplinary research groups encourage participants to broaden their understanding of science and the wider impact of astronomy across the globe. These projects serve as a pathway for those from non-scientific backgrounds to engage in astronomy, as well as promoting creativity and developing new perspectives among young people.

In this presentation we will share our learned experience as an international organisation on how to facilitate interdisciplinary research projects for young people. We will also share some examples of projects which worked (and didn’t work!), our reflections, and the feedback from participants engaging in these projects and how it has shaped their research skills and sense of perspective. I will also discuss the other ways we incorporate art in various forms throughout the camp as a compliment to the research offering, to encourage imagination, innovation and skill-sharing.

516 Teaching Astronomy with Visual Art, Poetry and Storytellling

Astronomy and astrophysics present extremely abstract concepts that secondary school children can find overwhelming. By teaching these concepts using STEAM learning we can not only give a better understanding of space but also nurture transferrable skills such as creativity, curiosity and experimentation in new contexts.

The Art of Astrophysics is an ongoing project in collaboration with Astrophysicists from the University of Oxford, principally Dr Sebastian von Hausegger, to show young people our universe from a new perspective.

So far the project has focussed on science communication but we are keen for young people's artistry to start informing research too.

We will talk about The MoSAIC's STEAM education journey so far, some of the highlights of the Art of Astrophysics project and some of the success stories that have lead to young people becoming more interdisciplinary learners.

We welcome contributions from astronomers, artists and “hybrids” at all levels that have engaged in or are curious about bridging art and science, and explore future collaborations.

Revealing the Milky Way with Gaia: Focus on Galactic dynamics in the Gaia era and beyond

Organisers: Paula Gherghinescu, Nicholas Walton; co organisers: Sioree Ansar, Giorgia Busso, Nigel Hambly, Jason Hunt, Sophia Lilleengen, Nicholas Rowell, George Seabroke, Mark Taylor

The ESA Gaia mission is creating a 3-D map of over two billion stars in our Milky Way. Gaia continues to provide new insights into our understanding of the Milky Way. In particular, the field of Galactic dynamics is an example of study that has been revolutionized with the availability of data from the Gaia mission.

It is now possible to directly map the structure and kinematics of all major Galactic components to unprecedented detail and precision. However, many traditional dynamical modelling methods use the Jeans theorem and start by assuming the galaxy is in dynamical equilibrium and axisymmetric.

While these models continue to be valuable in offering a’ big picture’ view up to large scales, their underlying assumptions can describe our Milky Way to first order only. For example, prominent non-axisymmetric structures such as the bar and spiral arms influence the dynamics of stars far across the disc, while the phase spiral (first revealed in the Gaia DR2 data), the warp, and the perturbation induced by the LMC in the outer halo highlight departures from equilibrium both locally and on the largest scales.

Current models do not fully capture the complexity of the data. With the increase in quantity and quality expected from Gaia DR4 and DR5 (supplemented with data from Euclid, LSST, and more) improved modelling methods are required.

The session will begin with an update from the Gaia:UK project team describing the latest scientific and technical performance of Gaia, developments in Gaia data acess, and giving a look ahead to the rapidly approaching seminal release of Gaia DR4, the full release of the 5 year Gaia nominal mission.

It will then focus more specifically in bringing together researchers working on a variety of novel numerical and analytical tools, as well as expertise in Gaia and associates survey data, to address challenges in improving our modelling techniques. Half block sessions will cover on (a) features and dynamics in the disc, (b) the dynamics of the halo, and (c) the Milky Way in a cosmological context.

517 Modelling the Milky Way structure: impact on stellar and gaseous dynamics

With the goal of investigating the role of the Galaxy’s large-scale dynamics on star formation, we use the hydrodynamical AREPO moving-mesh code to perform simulations of the Milky Way. Our models include a live stellar disc and bulge, a live dark matter halo, and a gaseous disc—evolved self-consistently with no fixed potentials and under isothermal equations of state.

We compare our results with 12CO and HI observations of the Milky Way by generating longitude-velocity diagrams of the projected gas surface densities. From these, we extract the skeletons of key features (spiral arms, bar) and terminal velocity contours, which we compare to observations via several diagnostic tools. Combining these, we identify a model that best reproduces the Milky Way’s main features. This model shows multiple transient spiral arms and an inner bar. The gas dynamics reveal a central “butterfly” pattern in radial velocity, characteristic of spiral galaxies, as well as clear streaming motions around spiral arms.

This best-fit model will serve as the base for future simulations including more detailed ISM physics (e.g. chemistry, star formation, feedback) to study how star formation is regulated in the Milky Way. In this talk, I will highlight the need for tailored dynamical models like this for interpreting Galactic-scale star formation. I will present results on the kinematics of gas and stars, and compare them to the latest Gaia DR3 findings—demonstrating the synergy between cutting-edge simulations and observational data in the Gaia era.

518 Milky Way - Sagittarius like interactions in the TNG50 cosmological simulation

The Sagittarius dwarf galaxy is without a doubt getting tidally disrupted by the Milky Way. Recent results from Gaia show that the Milky Way disc is far from equilibrium. Various works have shown that the interaction with Sagittarius can have a significant effect on unsettling the Galactic disc, resulting in many observed features like the Galactic warp, disc corrugation, spiral structure, phase space spirals, and even increased star-forming activity. However, many of these models assume an initial equilibrium, making the disc more susceptible to external perturbations. In my talk, I will present our recent, exciting results on how cosmologically evolved discs from the TNG50 simulation, which have never been in equilibrium, react to interactions similar to the one with Sagittarius.

Speaker: Marcin Semczuk (Universitat de Barcelona)

519 Inferring properties of the Milky Way and LMC using Simulation-Based Inference

The infall of the LMC into the Milky Way (MW) has caused significant disequilibrium throughout the MW. In particular, it has moved the MW's centre of mass and deformed its dark matter halo. There are only a handful of tailored MW—LMC simulations that can capture all aspects of this dynamical disequilibrium.

I will show how we can utilise much simpler rigid MW—LMC models to still constrain many properties of interest e.g., the masses of the MW and LMC.

I will use a ‘Simulation-Based Inference’ (SBI) approach to infer model parameters of the MW—LMC system. SBI is a powerful tool as it does not require likelihood functions to be defined. Instead, one can run many forward simulations to mimic observed quantities, and use data from surveys e.g., Gaia, DESI to extract the properties of the MW and LMC which are allowed given these observations.

I will show that using an SBI pipeline trained on a set of millions of rigid MW—LMC simulations is able to: i) accurately reproduce true parameters from MW—LMC that also include deformations despite that not being in our model and ii) place constraints on the MW mass, LMC mass, reflex velocity apex, and much more using stellar halo kinematic data from MW surveys.

This first application of SBI to the MW—LMC system shows a promising avenue to infer properties of both the MW and LMC without the need to run computationally intensive simulations.

Speaker: Richard Brooks (University College London)

520 The role of equilibrium dynamical models in understanding the formation histories of the Milky Way and its analogues

The Gaia spacecraft has brought our Milky Way into focus in an unprecedented way. The synergy with ground-based spectroscopic surveys has provided us with photometry, 6-D phase-space coordinates, and spectra for millions of stars. This rich data has highlighted the presence of departures from dynamical equilibrium, such as the phase-space spiral.

Despite these departures, equilibrium dynamical models can still provide a useful tool for understanding the formation of galaxies. I will show this with two examples using the Milky Way, M31, and Milky Way analogues as case studies. In the first example, I will present how we can use cosmological simulations of galaxies to measure the systematic uncertainties in derived dark matter mass distributions and velocity anisotropies in equilibrium dynamical modelling. In the second example, I will showcase the power of extended distribution functions, or eDFs, in modelling both our Milky Way and Milky Way analogues (MWAs) with integral-field unit data. In the former, eDFs neatly couple the selection function with the age, metallicity, and kinematic distribuions to reveal the intrinsic distributions. In the latter, eDFs offer a natural mechanism for modelling the coupled chemodynamical data encoded in IFU spectra. A final advantage offered by using analytical eDFs is that they can be easily related to aspects of formation history like the star formation history, thus offering a direct way of comparing MWAs.

Speaker: Payel Das (University of Surrey)

521 Dynamical streams in the local stellar halo

Co-moving groups of stars (streams) are well known in the velocity space of the disc near the Sun. Many are thought to arise from resonances with the Galactic bar or spiral arms. In this work, we search for similar moving groups in the velocity space of the halo, at low angular momentum. From the asymmetry of the radial velocity distribution $v_R$, we identify two inward-moving streams with $v_R<0$ and small $|v_\phi|$. These are projections of the 'chevrons' previously discovered in radial phase space $(R,v_R)$. A test particle simulation in a realistic Milky Way potential with a decelerating bar naturally produces analogues of these features, and they are observed across a wide range of metallicity. They are therefore very likely to be dynamical streams created by trapping in the bar's resonances. Specifically, they occupy regions of phase space where orbits are trapped in the corotation and outer Lindblad resonances respectively. By tracing these streams across a range of radii in $(R,v_R)$ space, we fit resonant orbits to their tracks in a flexible potential with variable bar pattern speed. This allows us to simultaneously constrain the mass profile of the Milky Way for $r\lesssim20$ kpc and the pattern speed $\Omegab$. We estimate the mass enclosed within $r=20$ kpc to be $M_{20}=(2.17\pm0.21)\times10^{11}M_\odot$, and the pattern speed to be $\Omega_\mathrm{b}=31.9_{-1.9}^{+1.8}$ km/s/kpc. Our fitted potential is in excellent agreement with previous results, while we favour a slightly slower pattern speed than most recent estimates.

522 Deep learning approaches to detecting dark matter in stellar streams

The fundamental nature of dark matter so far eludes direct detection experiments, but it has left its imprint in the population of low-mass sub-halos in the Milky Way (MW). Measurements of the MW phase space from observatories like Gaia will probe the lightest dark halos ever detectable (< 10^7 M_Sol) through their gravitational perturbations with thin tidal streams of stars. It is thus paramount that as much information as possible is extracted, while carefully accounting for the complex modelling uncertainties and instrumental systematics through detailed simulations. I will present a new approach to robust inference of fundamental physics from stellar stream data using graph neural networks to compress the full 6D phase space and normalising flows to infer posterior distributions. I will demonstrate that this deep learning method can improve constraints on halo properties by up to a factor of 100 compared to existing density power spectrum measurements. I will discuss plans to prepare this pipeline for upcoming Gaia data, in particular the modelling challenge.

Speaker: Keir Rogers (Imperial College London)

15:45 Fin