Description
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.
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...
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...
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...
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...
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 Sรฉrsic profile fitting and non-parametric morphological metrics.
NewHorizon and TNG50...
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...
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...
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...
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...
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...
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...
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...
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 (โcoresโ) are longstanding tensions with ฮCDM predic-
tions in the dwarf regime. However, if non-equilibrium effects are โmaskedโ...
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...
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...
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...
In recent years, there has been both an expansion in what we know about AGN and central black holes in dwarf galaxies, and a huge deluge of data from JWST about early black holes and galaxy evolution. Our research aims to use the new data about dwarf galaxies to constrain our models of AGN seeding, growth and feedback in GALFORM, the Durham semi-analytic model, and apply this updated model to...
Accurate distance measurements are crucial for understanding galaxies' stellar populations and dynamics. We present the globular cluster velocity dispersion (GCVD) method, a novel approach for measuring distances to galaxies. This method leverages the established relation between the absolute magnitudes and velocity dispersions of globular clusters (GCs). After testing the technique on 94...
Dwarf galaxies are extremely faint, limiting their direct study to the local universe (z โฒ 0.02). However, in galaxy-scale strong lensesโcharacterized by distinct features such as multiply imaged giant arcsโdwarf satellites within the lens galaxy can induce detectable gravitational perturbations in the background source's light. By carefully analyzing these perturbations, we can...
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 (DM) halo properties are extensively studied in cosmological simulations but are very challenging to estimate from observations. The DM halo density profile of observed galaxies is modelled using multiple probes that trace the dark matter potential. However, the angular momentum distribution of DM halos is still a subject of debate. In this study we investigate a method for...
The near-infrared Ks-band is essential for studying low surface brightness (LSB) structures, as it traces older stellar populations and offers valuable insights into the early Universe. Observing in this band is particularly important for faint galaxies with evolved stellar populations or significant dust extinction. VISTA, the largest near-infrared survey telescope, plays a crucial role in...
The scarcity of truly isolated quiescent dwarf galaxies (7 < (log$M_*/M_{\odot}$) < 9) is interpreted as evidence that becoming a satellite of a more massive halo is a necessary condition to quench star formation activity in these systems. In this study, we present a detailed analysis of environmental quenching using VLT-MUSE observations of a sample of 70+ dwarf galaxies from the MATLAS...
The star-formation rate density (SFRD) as a function of stellar mass is a useful descriptive and diagnostic for galaxy evolution as it links the SFR and galaxy stellar mass functions (GSMFs). It is a more complete measurement in observations and thus can be used to quantify the low-mass galaxy population over a cosmological volume. The SFRD is ideally measured using direct tracers of star...
It has been shown that the dynamics of the Milky Way satellites is determined not only by the MW but also significantly affected by the LMC. Recently, it has been demonstrated that the Tucana IV dwarf had a close passage (~4 kpc) with the LMC ~130 Myr ago. I will start this talk by describing the results of the orbit rewinding of the MW dwarfs, showing that Tucana IV was likely strongly...
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...
