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Title:
Density Profiles of Cold Dark Matter Substructure: Implications for the Missing-Satellites Problem
Authors:
Kazantzidis, Stelios; Mayer, Lucio; Mastropietro, Chiara; Diemand, Jürg; Stadel, Joachim; Moore, Ben
Affiliation:
AA(), AB(), AC(Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; ), AD(Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; ), AE(Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; ), AF(Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; )
Publication:
The Astrophysical Journal, Volume 608, Issue 2, pp. 663-679. (ApJ Homepage)
Publication Date:
06/2004
Origin:
UCP
ApJ Keywords:
Cosmology: Theory, Cosmology: Dark Matter, Galaxies: Halos, Methods: n-Body Simulations
DOI:
10.1086/420840
Bibliographic Code:
2004ApJ...608..663K

Abstract

The structural evolution of substructure in cold dark matter (CDM) models is investigated combining ``low-resolution'' satellites from cosmological N-body simulations of parent halos with N=107 particles with high-resolution individual subhalos orbiting within a static host potential. We show that, as a result of mass loss, convergence in the central density profiles requires the initial satellites to be resolved with N=107 particles and parsec-scale force resolution. We find that the density profiles of substructure halos can be well fitted with a power-law central slope that is unmodified by tidal forces even after the tidal stripping of over 99% of the initial mass and an exponential cutoff in the outer parts. The solution to the missing-satellites problem advocated by Stoehr et al. in 2002 relied on the flattening of the dark matter halo central density cusps by gravitational tides, enabling the observed satellites to be embedded within dark halos with maximum circular velocities as large as 60 km s-1. In contrast, our results suggest that tidal interactions do not provide the mechanism for associating the dwarf spheroidal (dSph) satellites of the Milky Way with the most massive substructure halos expected in a CDM universe. Motivated by the structure of our stripped satellites, we compare the predicted velocity dispersion profiles of Fornax and Draco to observations, assuming that they are embedded in CDM halos. We demonstrate that models with isotropic and tangentially anisotropic velocity distributions for the stellar component fit the data only if the surrounding dark matter halos have maximum circular velocities in the range 20-35 km s-1. If the dSphs are embedded within halos this large, then the overabundance of satellites within the concordance ΛCDM cosmological model is significantly alleviated, but this still does not provide the entire solution.
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