2006/08/31 by M. Gustafsson, Michael Gustafsson, Malcolm Fairbairn +2 · 8 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1103/physrevd.74.123522
published as Phys.Rev. D74 (2006) 123522 · 16 pages, 14 figures and 8 tables. Minor text improvements, typo corrections and an updated reference list to match the published version
openalex publication_date 2006/12/29 · arxiv created 2007/01/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 \ensuremathρDM\ensuremath∝r^\ensuremath-1.3\ifmmode±\else\textpm\fi0.2, 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 \ensuremathρDM\ensuremath∝r^\ensuremath-1.9\ifmmode±\else\textpm\fi0.2, with an indication of the inner logarithmic slope converging. Models of adiabatic contraction of dark matter halos due to the central buildup 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 dark matter halo contraction as compared to the Blumenthal et al. model, the fluxes from dark matter annihilation are 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\ifmmode±\else\textpm\fi0.11, with their flattening aligned with the central baryonic disks.