Might we eventually understand the origin of the dark matter velocity anisotropy?

Abstract

The density profile of simulated dark matter structures is fairly well-established, and several explanations for its characteristics have been put forward. In contrast, the radial variation of the velocity anisotropy has still not been explained. We suggest a very simple origin, based on the shapes of the velocity distributions functions, which are shown to differ between the radial and tangential directions. This allows us to derive a radial variation of the anisotropy profile which is in good agreement with both simulations and observations. One of the consequences of this suggestion is that the velocity anisotropy is entirely determined once the density profile is known. We demonstrate how this explains the origin of the γ-βrelation, which is the connection between the slope of the density profile and the velocity anisotropy. These findings provide us with a powerful tool, which allows us to close the Jeans equations.

10 pages, 7 figures, subm to apj

References in corpus (22)

• The Observed properties of Dark Matter on small spatial scales
• The Universal Rotation Curve of Spiral Galaxies. II The Dark Matter Distribution out to the Virial Radius
• A universal density slope - velocity anisotropy relation for relaxed structures
• Empirical Models for Dark Matter Halos. II. Inner profile slopes, dynamical profiles, and rho/sigma^3
• Spin-independent elastic WIMP scattering and the DAMA annual modulation signal
• Where are the ``Missing'' Galactic Baryons?
• The distribution function of dark matter in massive haloes
• The evolution of clusters in the CLEF cosmological simulation: X-ray structural and scaling properties
• Velocity distributions in clusters of galaxies
• The dynamical structure of dark matter haloes
• Circular velocity profiles of dark matter haloes
• The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure
• The nature of dark matter and the density profile and central behavior of relaxed halos
• Measurement of the dark matter velocity anisotropy in galaxy clusters
• Alas, the dark matter structures were not that trivial
• Dark Matter Halos: Velocity Anisotropy -- Density Slope Relation
• Measuring the dark matter velocity anisotropy in galaxy clusters
• What it takes to measure a fundamental difference between dark matter and baryons: the halo velocity anisotropy
• The dynamical structure of dark matter halos with universal properties
• Density Profiles of Collisionless Equilibria. II. Anisotropic Spherical Systems
• Phase-Space Density Profiles in Scale-Free Cosmologies
• Nature and Nurture in Dark Matter Halos

Cited by in corpus (21)

• Neutron Stars as Dark Matter Probes
• CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z=0.44 galaxy cluster MACS 1206.2-0847
• The Dark Matter at the End of the Galaxy
• A Parameter Space Exploration of Galaxy Cluster Mergers I: Gas Mixing and the Generation of Cluster Entropy
• Spherical galaxy models as equilibrium configurations in nonextensive statistics
• Concentration, Ellipsoidal Collapse, and the Densest Dark Matter haloes
• The dynamics of z~1 clusters of galaxies from the GCLASS survey
• The GOGREEN survey: the internal dynamics of clusters of galaxies at redshift 0.9-1.4
• Statistical mechanics of collisionless orbits. III. Comparison with N-body simulations
• Dense Dark Matter Hairs Spreading Out from Earth, Jupiter and Other Compact Bodies
• Dark matter capture by the Sun: revisiting velocity distribution uncertainties
• The temperature of hot gas in galaxies and clusters: baryons dancing to the tune of dark matter
• Towards a more rigorous treatment of uncertainties on the velocity distribution of dark matter particles for capture in stars
• Asymmetric velocity anisotropies in remnants of collisionless mergers
• Deriving galaxy cluster velocity anisotropy profiles from a joint analysis of dynamical and weak lensing data
• Determining all gas properties in galaxy clusters from the dark matter distribution alone
• Made-To-Measure Models of Self-Similar Triaxial Halos with Steep Inner Density Gradients
• Estimating the dark matter velocity anisotropy to the cluster edge
• A derivation of (half) the dark matter distribution function
• Dynamics of merging: Post-merger mixing and relaxation of an Illustris galaxy
• Cusped Mass Density Profiles and Magnification Ratios of Double Image Gravitational Lenses