On the Longevity of current epoch Compact Group-like Associations in a ΛCDM Cosmology

The survival time of initially compact associations of galaxy-size dark matter halos, obtained at the present epoch from a series of ΛCDM cosmological simulations, is studied by means of dynamical N-body simulations. The time evolution of such systems from the present epoch up to 5 Gyr into the future is followed. We find that out of 14 initial compact associations only 1 (≈ 10%) suffers a full merger, and the others still have at least two discernible members in such a time span, although they have suffered multiple mergers. Our results support the hypothesis that the majority of current compact galaxy groups will not suffer a complete merger within the next few gigayears, and that some of them (≈ 10%) may even evolve without a single merger. We conclude that no overmerging problem exists in compact groups.