DescriptionRecently, many new faint dwarf galaxies have been discovered around the Milky Way,including dozens of ultra-faint dwarf (UFD) galaxies—the smallest and most ancient galaxies known. We use cosmological hydrodynamic zoom-in simulations to study the formation and evolution of these galaxies. First, we introduce a new suite of high-resolution simulations of Milky Way-like hosts, enabling the study of UFDs in environments similar to those in which they have been discovered. We show that the simulated galaxies reproduce a variety of observed properties over orders of magnitude in luminosity. We further demonstrate that many of the properties of these simulated galaxies are influenced by interactions with their Milky Way-like hosts. Such interactions may contribute to the diversity seen in observed faint dwarfs.
Given the small potential wells of dwarf galaxies, they are very sensitive to the physicsof galaxy formation, much of which occurs on scales beneath our resolution. Therefore, we study how sub-grid models impact the properties of dwarf galaxies in the simulations. First, we update the treatment of the stellar initial mass function (IMF), which describes the distribution of stellar masses contained within each star particle. We implement a stochastically populated IMF, and show that it leads to burstier feedback, which suppresses star formation compared to a continuous treatment. Finally, we investigate how the underlying physics of star formation alters UFD properties by testing several different star formation models. We show that galaxy stellar metallicities are sensitive to changes between the runs, and can be paired with observations to constrain the models.