We investigate the structure of cold dark matter halos using advanced models of spherical collapse and accretion in an expanding universe. These are based on solving time-dependent equations for the moments of the phase-space distribution function in the fluid approximation; our approach includes non-radial random motions and, most importantly, an advanced treatment of both dynamical relaxation effects that take place in the infalling matter: phase-mixing associated with shell crossing and collective collisions related to physical clumpiness. We find self-similar solutions for the spherically averaged profiles of mass density ρ(r), pseudo phase-space density Q(r), and anisotropy parameter β(r). These profiles agree with the outcomes of state-of-the-art N-body simulations in the radial range currently probed by the latter; at smaller radii, we provide specific predictions. In the perspective provided by our self-similar solutions, we link the halo structure to its two-stage growth history and propose the following picture. During the early fast collapse of the inner region dominated by a few merging clumps, efficient dynamical relaxation plays a key role in producing closely universal mass density and pseudo phase-space density profiles; in particular, these are found to depend only weakly on the detailed shape of the initial perturbation and the related collapse times. The subsequent inside-out growth of the outer regions feeds on the slow accretion of many small clumps and diffuse matter; thus the outskirts are only mildly affected by dynamical relaxation but are more sensitive to asymmetries and cosmological variance.
Lapi, A., & Cavaliere, A. (2011). Self-Similar Dynamical Relaxation of Dark Matter Halos in an Expanding Universe. THE ASTROPHYSICAL JOURNAL, 743, 127.
|Tipologia:||Articolo su rivista|
|Citazione:||Lapi, A., & Cavaliere, A. (2011). Self-Similar Dynamical Relaxation of Dark Matter Halos in an Expanding Universe. THE ASTROPHYSICAL JOURNAL, 743, 127.|
|Settore Scientifico Disciplinare:||Settore FIS/05 - Astronomia e Astrofisica|
|Revisione (peer review):||Sì, ma tipo non specificato|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1088/0004-637X/743/2/127|
|Stato di pubblicazione:||Pubblicato|
|Data di pubblicazione:||2011|
|Titolo:||Self-Similar Dynamical Relaxation of Dark Matter Halos in an Expanding Universe|
|Autori:||Lapi, A; Cavaliere, A|
|Appare nelle tipologie:||01 - Articolo su rivista|