Asymmetric velocity anisotropies in remnants of collisionless mergers

Abstract

Dark matter haloes in cosmological N-body simulations are affected by processes such as mergers, accretion and the gravitational interaction with baryonic matter. Typically the analysis of dark matter haloes is performed in spherical or elliptical bins and the velocity distributions are often assumed to be constant within those bins. However, the velocity anisotropy, which describes differences between the radial and tangential velocity dispersion, has recently been show to have a strong dependence on direction in the triaxial halos formed in cosmological simulations. In this study we derive properties of particles in cones parallel or perpendicular to the collision axis of merger remnants. We find that the velocity anisotropy has a strong dependence on direction. The finding that the direction-dependence of the velocity anisotropy of a halo depends on the merger history, explains the existence of such trends in cosmological simulations. It also explains why a large diversity is seen in the velocity anisotropy profiles in the outer parts of high-resolution simulations of cosmological haloes.

arXiv comment19 pages, 15 figures, Resubmitted to JCAP after referee comments

References in corpus (28)

• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Measurements of Omega and Lambda from 42 High-Redshift Supernovae
• A Universal Density Profile from Hierarchical Clustering
• Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The Structure of Cold Dark Matter Halos
• The cosmological simulation code GADGET-2
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• A direct empirical proof of the existence of dark matter
• Modeling feedback from stars and black holes in galaxy mergers
• Clumps and streams in the local dark matter distribution
• The Shape of Dark Matter Halos: Dependence on Mass, Redshift, Radius, and Formation
• Velocity and spatial biases in CDM subhalo distributions
• The Phase-Space Density Profiles of Cold Dark Matter Halos
• Strong and weak lensing united III: Measuring the mass distribution of the merging galaxy cluster 1E0657-56
• The speed of the `bullet' in the merging galaxy cluster 1E0657-56
• A universal density slope - velocity anisotropy relation for relaxed structures
• Dynamical insight into dark-matter haloes
• Semi-analytical dark matter halos and the Jeans equation
• The Density and Pseudo-Phase-Space Density Profiles of CDM halos
• The Graininess of Dark Matter Haloes
• Statistical mechanics of collisionless orbits. I. Origin of central cusps in dark-matter halos
• Dark matter density profiles from the Jeans equation
• Numerical stability of a family of Osipkov-Merrit models
• Statistical mechanics of collisionless orbits. II. Structure of halos
• Statistical mechanics of collisionless orbits. III. Comparison with N-body simulations
• Might we eventually understand the origin of the dark matter velocity anisotropy?
• The haloes of merger remnants
• A statistical-mechanical explanation of dark matter halo properties

Cited by in corpus (10)

• Orbital anisotropy in cosmological haloes revisited
• The behaviour of shape and velocity anisotropy in dark matter haloes
• Towards a higher mass for NGC1052-DF2: an analysis based on full distribution functions
• Orbital distribution of infalling satellite halos across cosmic time
• Particle ejection during mergers of dark matter halos
• Stirring N-body systems: Universality of end states
• Estimating the dark matter velocity anisotropy to the cluster edge
• A derivation of (half) the dark matter distribution function
• A Gravitational Double Scattering Mechanism for Generating High Velocity Objects
• Stirring N-body systems II: Necessary conditions for the dark matter attractor