Semi-analytical predictions of density profiles for ΛCDM haloes

1st Experimental Lyceum of Athens, Ipitou 15, Plaka, 10557 Athens, Greece e-mail: hiotelis@ipta.demokritos.gr

Received: 5 May 2006
Accepted: 29 June 2006

Abstract

We combine the results of merger trees realizations, predicted by the extended Press-Schechter theory, to the assumption of “stable clustering” in order to calculate density profiles of dark matter haloes. Our results show that: 1) Haloes of different masses have different concentrations. More specifically, concentration is a decreasing function of the mass. The relation between concentration and virial mass predicted by our results is in good agreement with the predictions of large cosmological N-body simulations. 2) The slope of the density profile of dark matter haloes is flatter at the inner regions and steepens outwards. At a given fraction of the virial radius the slope (defined as minus the derivative of the logarithm of the density with respect to the logarithm of the radial distance) is a decreasing function of the virial mass of the halo. At 0.01 of the virial radius R_vir the slope ranges from 0.4 to 1.5 for masses in the range to . At distance R_vir the values of the slope are in the range 2.5 to 5.5. We note that the small values of the inner slope predicted in this paper are closer to the predictions of observations than the results of N-body simulations. 3) Comparing haloes of the same present day mass we found that: a) Haloes with large rate of recent mass increase, show flatter outer density profiles than those with small recent mass increase. b) The concentration becomes larger for increasing recent mass growth rate.