THE STRUCTURE OF GALAXY CLUSTERS IN VARIOUS COSMOLOGIES

We investigate the internal structure of clusters of galaxies in high- resolution N-body simulations of four different cosmologies. There is a higher proportion of disordered clusters in critical-density than in low-density universes, although the structure of relaxed clusters is very similar in each case, Crude measures of substructure, such as the shift in the position of the centre-of-mass as the density threshold is varied, can distinguish the two in a sample of just 20 or so cluste rs; it is harder to differentiate between clusters in open and flat mo dels with the same density parameter. Most clusters are in a quasi-ste ady state within the virial radius and are well-described by the densi ty profile of Navarro, Frenk & White.