Connecting the near and far: insights into reionisation-era faint galaxies from the formation histories of Local Group galaxies

Understanding the nature and physics of low-mass galaxies can help inform almost every aspect of galaxy formation and evolution. In this talk, I will highlight how studying galaxies in the Local Group, especially those in which we can observe resolved stellar populations, can probe not only the fundamental processes of their formation but also the nature of the faintest galaxies during the Epoch of Reionisation. A key open question about galaxies at z > 6 is the shape of the faint end of the Ultraviolet Luminosity Function (UVLF). However, even deep-field HST/JWST lensing surveys likely do not push deep enough to directly observe the faintest galaxies at these redshifts. A powerful alternative is the "near-far" approach, which leverages reconstructed star formation histories of low-mass galaxies in the Local Group in order to infer the faint-end UVLF at z > 6. I will present my work using the FIRE cosmological baryonic zoom-in simulations to test key uncertainties in this near-far method that might bias inferences of the high redshift UVLF. This includes modeling how low-mass galaxies in the proto-Local Group at z > 6 evolve to present day, and characterising their mergers, disruption, and survival. I will demonstrate how these results as well as current work in prep help test the fidelity of the near-far approach as a probe of faint galaxy populations during reionisation.

I will also discuss my work modeling crucial supernova feedback mechanisms in low-mass galaxies, especially in metal-poor stellar populations similar to those at high redshift. Using the FIRE simulations, I will show how metallicity-dependent Type Ia supernova rates can help us better understand the star formation histories andelemental abundances of these galaxies, thereby further informing their evolutionary mechanisms and connections to faint galaxies during reionisation. Finally, I will present exciting initial results on the properties of satellite galaxies in one of the highest resolution Milky Way-mass simulations to date, pushing the boundaries of what we can resolve and understand about galaxy formation in the lowest-mass regimes.