Nonspherical similarity solutions for dark halo formation
  We carry out fully 3-dimensional simulations of evolution from self-similar,
spherically symmetric linear perturbations of a Cold Dark Matter dominated
Einstein-de Sitter universe. As a result of the radial orbit instability, the
haloes which grow from such initial conditions are triaxial with major-to-minor
axis ratios of order 3:1. They nevertheless grow approximately self-similarly
in time. In all cases they have power-law density profiles and near-constant
velocity anisotropy in their inner regions. Both the power-law index and the
value of the velocity anisotropy depend on the similarity index of the initial
conditions, the former as expected from simple scaling arguments. Halo
structure is thus not "universal" but remembers the initial conditions. On
larger scales the density and anisotropy profiles show two characteristic
scales, corresponding to particles at first pericentre and at first apocentre
after infall. They are well approximated by the NFW model only for one value of
the similarity index. In contrast, at all radii within the outer caustic the
pseudo phase-space density can be fit by a single power law with an index which
depends only very weakly on the similarity index of the initial conditions.
This behaviour is very similar to that found for haloes formed from LCDM
initial conditions and so can be considered approximately universal.
