Description
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 โ surprisingly abundant bright ultra-high redshift galaxies, early SMBHs, and early quiescent galaxies, and unique chemical signatures โ 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.
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
The SKA is now under construction, and its two main mid-frequency precursor instruments, the Australian SKA Pathfinder and MeerKAT radio telescopes, are in full swing. In particular, ASKAP is conducting all-sky surveys of the neutral hydrogen (HI) content in emission and absorption (WALLABY and FLASH surveys respectively), while MeerKAT probes select fields or targets to far deeper levels...
Fuzzy Dark Matter with an explicitly non-zero quartic self-interaction (gFDM) is shown to be a viable model for simultaneously fitting 17 dark-matter-dominated galaxies from the SPARC database, constraining both the boson mass, $m$, and the self-coupling constant, $g$, to values within the range $\log_{10}\left(\frac{m}{\mathrm{eV}/c^2}\right) = \log_{10}(1.98)-22^{+0.8}_{-0.6}$ and...
The cosmic 21-cm signal is a rich probe of our cosmic history, especially the Cosmic Dawn when the earliest stars and galaxies form, and the subsequent Epoch of Reionization. Many attempts are being made to capture this unique signal with increasingly good sensitivity through interferometers like HERA and NenuFAR, and monopole antennas like EDGES, SARAS and REACH. In parallel, the ambitious...
We present KIARA-RT, a fully coupled cosmological radiative transfer hydrodynamical simulation designed to model the Epoch of Reionization (EoR). Our framework builds upon the well-established KIARA galaxy formation modelโan advanced successor to SIMBAโand integrates the moment-based radiative transfer solver GEAR-RT within the SWIFT cosmological code. To further enhance the accuracy of early...
Large mock galaxy catalogues are essential to our understanding of rare environments, galaxy clustering, and cosmic variance. However, large simulations are prohibitively expensive to run without making compromises on the resolution and/or complexity of physics. By learning the galaxy-halo connection in zoom simulations, we can map galaxies onto large N-body simulations at low computational...
Historic merger events are expected to leave imprints of their collisions in the stellar haloโs phase space and chemodynamics. However, interpreting such imprints is complicated by the complex hierarchical history expected in LCDM (Rey M. P.et al. , 2023, MNRAS, 521, 995 10.1093/mnras/stad513). Here, we explore the impact of merging within the PARADIGM simulations (Joshi G. D. et al ,...
