N-body simulations of small galaxy groups

A series of N-body simulations aimed at studying the dynamics of small groups of galaxies is presented. In particular, our results are compared with the dynamical properties of Hickson's compact groups (HCG). "Maximum expansion' and virial initial conditions are tested, and no primordial common dark halo is considered. The properties of small galaxy groups are very well reproduced, and those of Hickson's groups are well reproduced for the most advanced stage of collapsing groups. We find no overmerging problem in our simulations. An important fraction of groups (similar to 40%) initially in virial equilibrium can last for similar to 10 Gyr without complete merging. These results provide an alternative solution to the overmerging expected in Hickson's compact groups. Also, the mass-to-light ratio of HCG are probably similar to those found in clusters, suggesting that both kinds of systems have about the same fraction of barionic to total mass.