High resolution cosmological N-body simulations of four galaxy-scale dark matter halos are compared to corresponding N-body/hydrodynamical simulations containing dark matter , stars and gas .
The simulations without baryons share features with others described in the literature in that the dark matter density slope continuously decreases towards the center , with a density \rho _ { DM } \propto r ^ { -1.3 \pm 0.2 } , at about 1 % of the virial radius for our Milky Way sized galaxies .
The central cusps in the simulations which also contain baryons steepen significantly , to \rho _ { DM } \propto r ^ { -1.9 \pm 0.2 } , with an indication of the inner logarithmic slope converging .
Models of adiabatic contraction of dark matter halos due to the central build-up of stellar/gaseous galaxies are examined .
The simplest and most commonly used model , by Blumenthal et al . , is shown to overestimate the central dark matter density considerably .
A modified model proposed by Gnedin et al . is tested and it is shown that while it is a considerable improvement it is not perfect .
Moreover it is found that the contraction parameters in their model not only depend on the orbital structure of the dark-matter–only halos but also on the stellar feedback prescription which is most relevant for the baryonic distribution .
Implications for dark matter annihilation at the galactic center are discussed and it is found that although our simulations show a considerable reduced halo contraction as compared to the Blumenthal et al . model , the fluxes from dark matter annihilation is still expected to be enhanced by at least a factor of a hundred as compared to dark-matter–only halos .
Finally , it is shown that while dark-matter–only halos are typically prolate , the dark matter halos containing baryons are mildly oblate with minor-to-major axis ratios of c / a = 0.73 \pm 0.11 , with their flattening aligned with the central baryonic disks .