Asymmetric velocity anisotropies in remnants of collisionless mergers
  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.
