Semi-analytical predictions of density profiles for ΛCDM haloes

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 5 × 10 9 h −1 M to 10 14 h −1 M . 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.

Empirical Models for Dark Matter Halos. II. Inner Profile Slopes, Dynamical Profiles, and ?/?3

“…Clearly, the apparent inconsistency between the inner profile slope of dark matter halos generated from ÃCDM N-body simulations and observations of real galaxies is reduced on replacement of the NFW model with the (better fitting) Einasto model. What is also apparent is that one can expect a range of different slopes inside 1 kpc (see also Hiotelis 2006), although this in itself does not imply a nonuniversal density profile. The largest study to date of (165) low-mass galaxies found inner logarithmic slopes ranging from À0:22 AE 0:08 to À0:28 AE 0:06 for various subsamples of the data (Spekkens et al 2005).…”

On the spin distributions of ΛCDM haloes

“…Hiotelis & Del Popolo (2006) showed that using the EC model, formation times are shifted to smaller values than those predicted by a spherical collapse model. Additionally, EC model, combined with the 'stable clustering' hypothesis, was used in order to study density profiles of dark matter haloes (Hiotelis 2006). The resulting density profiles at the central regions of haloes have the interesting feature to be closer to the results of observations than the results of N-body simulations.…”

CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of thez= 0.44 galaxy cluster MACS J1206.2-0847

“…A general consensus is growing that the universal NFW-like shape, at least in the central regions, is the result of the initial, fast assembly phase of halos (Huss et al 1999b;Manrique et al 2003;Arad et al 2004;Tasitsiomi et al 2004;Lu et al 2006;El-Zant 2008;Wang & White 2009;, characterized by dynamical processes such as violent and collective relaxation, and phase and chaotic mixing (Hénon 1964;Lynden-Bell 1967;Merritt 2005;Henriksen 2006, and references therein). The following slower accretion phase may be responsible for the outer slope of the density profile (Tasitsiomi et al 2004;Lu et al 2006;Hiotelis 2006). Halos would obtain the same, universal density profile independently of details about their collapse (El-Zant 2008;Wang & White 2009) and subsequent merger histories (Dehnen 2005;Kazantzidis et al 2006;El-Zant 2008;Wang & White 2009;Salvador-Solé et al 2012).…”