2002/05/31 by Avishai Dekel, Itai Arad, Jonathan Devor +1 · 55 citations
Mathematics · Physics and Astronomy · #Astronomy #Astrophysics #Cosmology and Gravitation Theories #Cusp (singularity) #Dark Matter and Cosmic Phenomena #Flattening #Galaxies: Formation, Evolution, Phenomena #Galaxy #Geometry #Halo #Halo mass function #Mathematics #Physics #astro-ph
paper · pdf · doi:10.1086/374328
published in The Astrophysical Journal 588(2), 680-695 (IOP Publishing) · 37 pages, Latex, aastex.cls, revised, ApJ, 588, in press
arxiv created 2003/01/27 · openalex publication_date 2003/05/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We propose a model for how the buildup of dark halos by merging satellites produces a characteristic inner cusp, with a density profile ρ ∝ r , where α in → α as ≳ 1, as seen in cosmological N -body simulations of hierarchical clustering scenarios. Dekel, Devor, & Hetzroni argue that a flat core of α in < 1 exerts tidal compression that prevents local deposit of satellite material; the satellite sinks intact into the halo center, thus causing a rapid steepening to α in > 1. Using merger N -body simulations, we learn that this cusp is stable under a sequence of mergers and derive a practical tidal mass transfer recipe in regions where the local slope of the halo profile is α > 1. According to this recipe, the ratio of mean densities of the halo and initial satellite within the tidal radius equals a given function ψ(α), which is significantly smaller than unity (compared to being ~1 according to crude resonance criteria) and is a decreasing function of α. This decrease makes the tidal mass transfer relatively more efficient at larger α, which means steepening when α is small and flattening when α is large, thus causing convergence to a stable solution. Given this mass transfer recipe, linear perturbation analysis, supported by toy simulations, shows that a sequence of cosmological mergers with homologous satellites slowly leads to a fixed-point cusp with an asymptotic slope α as > 1. The slope depends only weakly on the fluctuation power spectrum, in agreement with cosmological simulations. During a long interim period the profile has an NFW-like shape, with a cusp of 1 < α in < α as . Thus, a cusp is enforced if enough compact satellite remnants make it intact into the inner halo. In order to maintain a flat core, satellites must be disrupted outside the core, possibly as a result of a modest puffing up due to baryonic feedback.