Dissipationless collapse of galaxies and initial conditions

This paper reports on the results of a number of simulations of dissipationless collapse using new numerical methods which permit the achievement of high central densities. A total of 64 simulations were run, starting from a wide range of initial conditions. The density and velocity profiles show a strong dependence on the initial kinetic energy of the particles, but appear only weakly dependent upon the initial clumpiness of the system. Systems started at low temperatures yield density profiles which are in agreement with observed galaxy profiles over a large proportion of their mass and reach central densities comparable to observed galaxies. For these systems, the most inhomogeneous models are best fit by Hubble profiles while smoother systems are closer to a de Vaucouleurs law. Ellipticities up to E4 are obtained without recourse to anisotropic initial conditions. Velocity profiles show marked anisotropy outside the half-mass radius of most systems.