A statistical-mechanical explanation of dark matter halo properties

Abstract

Cosmological N-body simulations have revealed many empirical relationships of dark matter halos, yet the physical origin of these halo properties still remains unclear. On the other hand, the attempts to establish the statistical mechanics for self-gravitating systems have encountered many formal difficulties, and little progress has been made for about fifty years. The aim of this work is to strengthen the validity of the statistical-mechanical approach we have proposed previously to explain the dark matter halo properties. By introducing an effective pressure instead of the radial pressure to construct the specific entropy, we use the entropy principle and proceed in a similar way as previously to obtain an entropy stationary equation. An equation of state for equilibrated dark halos is derived from this entropy stationary equation, by which the dark halo density profiles with finite mass can be obtained. We also derive the anisotropy parameter and pseudo-phase-space density profile. All these predictions agree well with numerical simulations in the outer regions of dark halos. Our work provides further support to the idea that statistical mechanics for self-gravitating systems is a viable tool for investigation.

5 pages, 4 figures, Accepted by A&A

References in corpus (6)

• Statistical mechanics and dynamics of solvable models with long-range interactions
• A universal density slope - velocity anisotropy relation for relaxed structures
• Statistical mechanics of collisionless orbits. I. Origin of central cusps in dark-matter halos
• Secondary Infall and the Pseudo-Phase-Space Density Profiles of Cold Dark Matter Halos
• Entropy principle and complementary second law of thermodynamics for self-gravitating systems
• Simple Models for the Distribution of Dark Matter

Cited by in corpus (10)

• Testing phenomenological and theoretical models of dark matter density profiles with galaxy clusters
• Asymmetric velocity anisotropies in remnants of collisionless mergers
• Equilibrium statistical mechanics for self-gravitating systems: local ergodicity and extended Boltzmann-Gibbs/White-Narayan statistics
• Saddle-point entropy states of equilibrated self-gravitating systems
• Power law pseudo phase-space density profiles of dark matter halos: fluke of physics?
• Statistical Mechanics of Collisionless Orbits. V. The approach to equilibrium for idealized self-gravitating systems
• Fluid-like entropy and equilibrium statistical mechanics of self-gravitating systems
• Second-order solutions of the equilibrium statistical mechanics for self-gravitating systems
• Statistical computation of Boltzmann entropy and estimation of the optimal probability density function from statistical sample
• Chaos in violent relaxation dynamics. Disentangling micro- and macro-chaos in numerical experiments of dissipationless collapse