ARE GROUPS OF GALAXIES VIRIALIZED SYSTEMS

Groups are systems of galaxies with crossing times t(cr) much smaller than the Hubble time. Most of them have t(cr) < 0.1H-0(-1). The usual interpretation is that they are in virial equilibrium. We compare the data of the group catalog [Ramella et al., ApJ, 344, 57 (1989)] selected from the CfA redshift survey extension with different N-body models. We show that the distributions of kinematic and dynamical quantities of the groups in the CfA catalog can be reproduced by a single collapsing group observed along different line of sights. This result shows that (a) projection effects dominate the statistics of these systems, and (b) observed groups of galaxies are probably still in the collapse phase.