Properties of groups of galaxies in the vicinity of massive clusters

This work analyses the properties of groups of galaxies in the vicinity of clusters. On the basis of a very large public Virgo Consortium Simulation, we identified systems of galaxies in a wide range of masses. Systems with masses greater than Mcut= 4 × 1014 M⊙h−1 are considered ‘hosts’, whereas smaller systems are taken as groups. Our results show that group properties are affected by the proximity of massive hosts. Physical properties such as velocity dispersion, internal energy (E) and virial radius, show an increment, whereas the mean density decreases as the host–group distance decreases. By analysing groups with different properties, we find that the low mass and the weakly bound (E > 0) subsamples are strongly affected by the presence of the host; on the other hand, massive groups and groups with E < 0 do not show dependence on the host–group distance. Using a sample of groups identified in the final version of the 2dF Galaxy Redshift Survey, we find a very similar velocity dispersion behaviour in the observational data compared to results in the simulation. We also study the dependence of the group velocity dispersion on the host masses in both observations and simulation, and we find that the larger the host mass, the higher the effect on its vicinity.