Structure of Galactic Dark Halos and Observational Prospects for Identifying the Nature of Dark Matter

Abstract

We study the internal structure of galactic size dark matter halos in the standard Λ Cold Dark Matter model under the assumption that cold dark matter consists of light neutralinos whose annihilation cross section is large. We use high resolution cosmological hydrodynamic simulations which include radiative cooling, starformation and supernova feedback effects. We show that the dissipative processes generally act as steepening the dark matter density profile, whereas supernova feedback mitigates the effect. However, when all of the processes are included, we still find many subhalos that have a steep (∝ r−1.5−2) density profiles. Such subhalos may be bright sources of γ-ray via pair-annihilation of neutralinos. We also find poor correlation between the stellar velocity dispersion profile and the underlying dark matter density profiles of subhalos. Observations of stellar velocity dispersions need to be interpreted with caution.