Secondary infall and the pseudo-phase-space density profiles of cold dark matter haloes

作者：Ludlow Aaron D^*; Navarro Julio F; Springel Volker; Vogel**erger Mark; Wang Jie; White Simon D M; Jenkins Adrian; Frenk Carlos S

来源：Monthly Notices of the Royal Astronomical Society, 2010, 406(1): 137-146.

DOI：10.1111/j.1365-2966.2010.16678.x

• methods: numerical
• dark matter

We use N-body simulations to investigate the radial dependence of the density, , and velocity dispersion, Sigma, in cold dark matter (CDM) haloes. In particular, we explore how closely Q equivalent to /Sigma 3, a surrogate measure of the phase-space density, follows a power law in radius. Our study extends earlier work by considering, in addition to spherically averaged profiles, local Q estimates for individual particles, Q(i); profiles based on the ellipsoidal radius dictated by the triaxial structure of the halo, Q(i)(r';); and by carefully removing substructures in order to focus on the profile of the smooth halo, Qs. The resulting Qs(i)(r';) profiles follow closely a power law near the centre, but show a clear upturn from this trend near the virial radius, r(200). The location and magnitude of the deviations are in excellent agreement with the predictions from Bertschinger';s spherical secondary-infall similarity solution. In this model, Q proportional to r-1.875 in the inner, virialized regions, but departures from a power-law occur near r(200) because of the proximity of this radius to the location of the first shell crossing - the shock radius in the case of a collisional fluid. Particles there have not yet fully virialized, and so Q departs from the inner power-law profile. Our results imply that the power-law nature of Q profiles only applies to the inner regions and cannot be used to predict accurately the structure of CDM haloes beyond their characteristic scale radius.

• 出版日期2010-7-21