Anisotropic q-Gaussian velocity distributions in LambdaCDM halos

Дата и время публикации : 2013-10-24T20:02:43Z

Авторы публикации и институты :
Leandro J. Beraldo
Gary A. Mamon
Manuel Duarte
Sébastien Peirani
Gwenaël Boué

Ссылка на журнал-издание: Ссылка на журнал-издание не найдена
Коментарии к cтатье: submitted to MNRAS, 10 pages, fixed 1st author name
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO, astro-ph.GA

Краткий обзор статьи: The knowledge of the velocity distribution function (VDF) of dark matter (DM) halos is required for calibrating the direct DM detection experiments and useful for recovering the mass profile from the observed distribution of tracers in projected phase space when the VDF has unknown anisotropy. Unfortunately, the VDF of halos in LambdaCDM dissipationless cosmological simulations is still poorly known. We consider the q-Gaussian (Tsallis) family of VDFs, among which the Gaussian is a special case. We extend the q-Gaussian to anisotropic VDFs by considering the isotropic set of dimensionless spherical velocity components normalized by the velocity dispersion along that component. We test our anisotropic VDF on 90 cluster-mass halos of a dissipationless cosmological simulation. While our anisotropic q-Gaussian model adequately reproduces the VDF averaged in spherical shells with radii greater than 2 virial radii, no q-Gaussian model can adequately represent the VDF in spherical shells of radius smaller than 2 virial radii, for which the distribution of dimensionless normalized velocity moduli is flatter than any q-Gaussian can allow. Nevertheless, the anisotropic q-Gaussian fits significantly better the simulated VDF than the commonly used Maxwellian (Gaussian) distribution, at all radii except near one-tenth of the virial radius. Beyond one-tenth of a virial radius, the radial variation of non-Gaussianity diverges between the mean fits and the fit on a random stack of halos, a feature that appears to be the consequence of the triaxiality of individual halos. We provide a parametrization of the modulation of the non-gaussianity parameter with radius for both the mean fits and the fit of the stacked halo.

Category: Physics