Density Profiles of Collisionless Equilibria. I. Spherical Isotropic Systems

Abstract

We investigate the connection between collisionless equilibria and the phase-space relation between density $\rho$ and velocity dispersion $\sigma$ found in simulations of dark matter halo formation, $F=\psd \propto r^{-α}$. Understanding this relation will shed light on the physics relevant to collisionless collapse and on the subsequent structures formed. We show that empirical density profiles that provide good fits to N-body halos also happen to have nearly scale-free \psd distributions when in equilibrium. We have also done a preliminary investigation of variables other than $r$ that may match or supercede the correlation with $F$. In the same vein, we show that $\rho /{\sigma }^m$, where $m=3$ is the most appropriate combination to use in discussions of the power-law relationship. Since the mechanical equilibrium condition that characterizes the final systems does not by itself lead to power-law $F$ distributions, our findings prompt us to posit that dynamical collapse processes (such as violent relaxation) are responsible for the radial power-law nature of the \psd distributions of virialized systems.

21 pages, 8 fig. (2 new), accepted by ApJ, a PDF version with full resolution figures can be found at http://www.astro.umn.edu/~barnes/research/astroph.html

References in corpus (17)

• A Universal Density Profile from Hierarchical Clustering
• The Structure of Cold Dark Matter Halos
• The Inner Structure of LambdaCDM Halos III: Universality and Asymptotic Slopes
• Resolving the Structure of Cold Dark Matter Halos
• Velocity and spatial biases in CDM subhalo distributions
• The Phase-Space Density Profiles of Cold Dark Matter Halos
• A dynamical model for the distribution of dark matter and gas in galaxy clusters
• Convergence and scatter of cluster density profiles
• A Universal Density Profile for Dark and Luminous Matter?
• A universal density slope - velocity anisotropy relation for relaxed structures
• Halo Cores and Phase Space Densities: Observational Constraints on Dark Matter Physics and Structure Formation
• Dynamical insight into dark-matter haloes
• On the physical origin of dark matter density profiles
• Semi-analytical dark matter halos and the Jeans equation
• Triaxial stellar systems following the r^{1/n} luminosity law: an analytical mass-density expression, gravitational torques and the bulge/disc interplay
• Velocity dispersion profile in dark matter halos
• Scalelengths in Dark Matter Halos

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• On Universal Halos and the Radial Orbit Instability
• Secondary Infall and the Pseudo-Phase-Space Density Profiles of Cold Dark Matter Halos
• The dynamical structure of dark matter haloes
• Dark Matter Equilibria in Galaxies and Galaxy Systems
• Secondary infall and dark matter haloes
• Fingerprints of the initial conditions on the density profiles of cold and warm dark matter haloes
• Evolution of the Dark Matter Phase-Space Density Distributions of LCDM Halos
• Non--power law behavior of the radial profile of phase--space density of halos
• Galaxy Kinematics and Mass Calibration in Massive SZE Selected Galaxy Clusters to z=1.3
• Influence of baryons on the orbital structure of dark matter haloes
• A theorem on central velocity dispersions
• Density Profiles of Collisionless Equilibria. II. Anisotropic Spherical Systems
• Power-laws and Non-Power-laws in Dark Matter Halos
• A Universal Power-law Profile of Pseudo-Phase-Space Density-like Quantities in Elliptical Galaxies
• Merger as Intermittent Accretion
• Effects of Angular Momentum on Halo Profiles
• Distribution Function in Center of Dark Matter Halo