Galaxy Groups - Sample-Dependence of Virial Properties

Extending a previous study on Turner and Gott's (1976) galaxy groups, we discuss the sample of groups selected by de Vaucouleurs (1975) to investigate the stability of some results concerning the virial parameters of the groups of galaxies. As for Turner and Gott's groups, the values of the virial parameters of galaxy groups are largely insensitive to different weighting procedures both in the velocity equipartition and in the energy equipartition dynamical hypotheses. The comparison between the two above-mentioned samples of groups shows that only the distribution functions of the virial radii differ significantly, while the distribution functions of the velocity dispersion and the mass-to-luminosity ratio do not. A dynamical status near velocity equipartition is favoured for the groups of galaxies.