UC Irvine

The Λ cold dark matter (DM) model successfully explains the distribution of large scale structure and the cosmic microwave background but, there are several problems concerning the distribution of DM on sub-galactic scales. Robust measurements of the distribution of DM in low mass dwarf galaxies are key to understand the true nature of DM. In this work, we present two new techniques for characterizing the kinematics of dispersion supported systems. The first method identifies localized kinematic substructure in line-of-sight velocity data while the second separates global stellar populations utilizing metallicty, line-of-sight velocity, and spatial information. We apply the first method to the dwarf spheroidal galaxy Ursa Minor and find two localized kinematic substructures at high significance. We present new Keck/DEIMOS spectroscopic observations of Ursa Minor, motivated by the previous detection, which form the largest spectroscopic data set of Ursa Minor. With the new data, we identify two chemodynamical stellar population at high significance with distinct kinematic, metallicity, and spatial distributions. By utilizing the dynamics of multiple stellar populations we break halo profile degeneracies and find the DM slope is more consistent with a ‘cored’ halo than a ‘cuspy’ halo. We present a complementary study comparing a large sample of literature rotation curves to dark matter halos influenced by baryonic processes. The analysis suggests that baryonic processes are an inconsistent solution to the ‘core-cusp’ problem.