MERGERS OF COLLISIONLESS SYSTEMS

The hierarchical clustering scenario is examined by merging haloes of collisionless particles under controlled conditions. Each simulation contains 16 000 particles, which gives a finer spatial resolution than in previous work. We find that dark matter haloes can grow homologously, obeying simple scaling laws. All the mergers tend towards a single density profile, which in our case closely resembles that given by de Vaucouleurs. The high resolution of our simulations also allows us to look at the resultant core structure of our haloes. We find that the central density is close to the maximum value allowed by phase-space constraints, indicating a smaller core radius in the dark matter than is generally assumed. The expected deviations from our results, given more realistic initial conditions, are discussed.