1203.4240 (Joe Wolf et al.)

Dark matter concentrations and a search for cores in Milky Way dwarf satellites    [PDF]

Joe Wolf, James S. Bullock

We investigate the mass distributions within eight classical Milky Way dwarf spheroidal galaxies (MW dSphs) using an equilibrium Jeans analysis and we compare our results to the mass distributions predicted for subhalos in dissipationless \Lambda CDM simulations. In order to match the dark matter density concentrations predicted, the stars in these galaxies must have a fairly significant tangential velocity dispersion anisotropy (\beta ~-1.5). For the limiting case of an isotropic velocity dispersion (\beta =0), the classical MW dSphs predominantly prefer to live in halos that are less concentrated than \Lambda CDM predictions. We also investigate whether the dSphs prefer to live in halos with constant density cores in the limit of isotropic velocity dispersion. Interestingly, even in this limit, not all of the dSphs prefer large constant-density cores: the Sculptor dSph prefers a cusp while Carina, Draco and Leo I prefer cores. The other four dSphs do not show a statistically significant preference for either cuspy or cored profiles. Finally, we re-examine the hypothesis that the density profiles of these eight MW dSphs can be quantified by a common dark matter halo.

View original: http://arxiv.org/abs/1203.4240