UC Davis

Understanding the nature and physics of low-mass galaxies can help inform almost every aspect of galaxy formation and evolution. In this work, I 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 at early cosmic times. A key open question about galaxies at z > 6 is the faint-end slope of the ultraviolet luminosity function (UVLF) or the low-mass slope of the stellar mass function (SMF). 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, is a powerful alternative to direct observations of faint high-redshift galaxies. I discuss my work using the FIRE-2 cosmological baryonic zoom-in simulations to characterize how well this near-far method recovers the high-redshift UVLF/SMF. This includes modeling how low-mass galaxies in the proto-Local Group at z > 6 evolve to present day, and characterizing their mergers, disruption, and survival. My results show that the near-far technique does provide accurate constraints on the faint/low-mass end of the reionization-era UVLF/SMF, and make forecasts for which galaxies in the Local Group can best inform the high-redshift UVLF/SMF via their fossil records. In the second half of this work, I 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-2 simulations, I show how metallicity-dependent Type Ia supernova rates can help us better model the star formation histories and elemental abundances of these galaxies, and further inform their evolutionary mechanisms and connections to faint galaxies during reionization.