1205.1799 (Martin Sparre et al.)

Asymmetric velocity anisotropies in remnants of collisionless mergers    [PDF]

Martin Sparre, Steen H. Hansen

Dark matter haloes in cosmological N-body simulations are affected by processes such as mergers, accretion and the gravitational interaction with baryonic matter. In typical analyses of dark matter haloes, the velocity distributions are assumed to be spherically symmetric. The validity of this assumption has, however, not been explicitly tested. We derive properties of particles in cones parallel or perpendicular to the collision axis of merger remnants. We find that the velocity anisotropy, which describes differences in the radial and tangential velocity dispersion, has a strong dependence on direction. The finding that the direction-dependence of the velocity anisotropy of a halo depends on the merger history, explain why a large diversity is seen in the velocity anisotropy profiles in the outer parts of high-resolution simulations of cosmological haloes.

View original: http://arxiv.org/abs/1205.1799