Abstract

The combined progress of observation and numerical simulation has sharpened our view of small-scale cosmological structure (linear scales smaller than ~1 Mpc) and brought to light several potential discrepancies between theoretical predictions and observations: dwarf galaxies are generally less dense and less abundant than might be naively expected in the now standard LCDM cosmological model. Much of this disagreement comes from comparing dissipationless LCDM simulations with observations. Many groups now find that star formation feedback can significantly affect the density structure of low-mass galaxies even if the gravitational potential is dark-matter-dominated. In this thesis, I employ fully hydrodynamical, cosmological simulations of dwarf galaxies that serve as prime candidates to test the ability of baryonic feedback to alleviate the small scale issues that face LCDM. I produce a definitive suite of cosmological simulations of fifteen dwarf galaxies, all having a halo mass ~10^10 Msun, precisely where we expect dwarfs to be sensitive probes of dark matter physics and galaxy evolution.  At this set halo mass we find that stellar mass at z=0 is strongly correlated with central halo density or maximum circular velocity Vmax, both of which are tightly linked to halo formation time. The stellar populations of these dwarf galaxies at z=0 are formed essentially entirely "in situ": over 90% of the stellar mass is formed in the main progenitor in all but two cases, and virtually all galaxy mergers occur prior to z~3, contributing uniformly ancient populations. We also simulate our suite of dwarf galaxies across a range of possible alternative dark matter candidates that aim to alleviate the small scale issues that remain even with the inclusion of baryons. Not only do we find that all our simulated dwarfs fall on a similar Mstar-R_1/2 relation, regardless of the underlying version of DM, but also that our dwarfs with visibly smaller dwarfs may be residing in larger halos than originally expected. While baryonic feedback does not appear as effective in alternate theories of DM, self-interaction still produces lower inner rotation curves and appears important for matching the low inner circular velocities of certain Local Field dwarfs that do not appear compatible with our suite of LCDM dwarfs.