Asymmetric velocity anisotropies in remnants of collisionless mergers
arXiv:1205.1799 · doi:10.1088/1475-7516/2012/07/042
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.
19 pages, 15 figures, Resubmitted to JCAP after referee comments
References in corpus (8)
- A direct empirical proof of the existence of dark matter
- 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
- The Graininess of Dark Matter Haloes
- Statistical mechanics of collisionless orbits. I. Origin of central cusps in dark-matter halos
- Statistical mechanics of collisionless orbits. III. Comparison with N-body simulations
- The haloes of merger remnants