Nature and Nurture in Dark Matter Halos

Abstract

Cosmological simulations consistently predict specific properties of dark matter halos, but these have not yet led to a physical understanding that is generally accepted. This is especially true for the central regions of these structures. Recently two major themes have emerged. In one, the dark matter halo is primarily a result of the sequential accretion of primordial structure (ie `Nature'); while in the other, dynamical relaxation (ie `Nurture') dominates at least in the central regions. Some relaxation is however required in either mechanism. In this paper we accept the recently established scale-free sub-structure of halos as an essential part of both mechanisms. Consequently; a simple model for the central relaxation based on a self-similar cascade of tidal interactions, is contrasted with a model based on the accretion of adiabatically self-similar, primordial structure. We conclude that a weak form of this relaxation is present in the simulations, but that is normally described as the radial orbit instability.

25 pages, 3 figures, fig with parts 1 to d, fig 3 with parts a to d

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Cited by in corpus (7)

• Theoretical dark matter halo density profile
• Might we eventually understand the origin of the dark matter velocity anisotropy?
• Black holes and Galactic density cusps -- I. Radial orbit cusps and bulges
• The double-power approach to spherically symmetric astrophysical systems
• Black Holes and Galactic Density Cusps Spherically Symmetric Anisotropic Cusps
• A derivation of (half) the dark matter distribution function
• Entropy plateaus can emerge from gas replacement at a characteristic halo mass in simulated groups and clusters of galaxies