Groups of galaxies. IV. Effect of observational selection on the relationship between the characteristics and distance of groups and a comparison with the groups of Geller and Huchra

摘要

The effect of observational selection on the relationship between the characteristics of groups of galaxies and their distances is discussed in this paper. For our groups the dependence of the pairwise distance between the members on the distance of the group is just that. For the groups of Geller and Huchra, on the other hand, the analogous dependence is distorted by the effect of their selection criteria for groups of galaxies. The average dispersion of the radial velocities of the galaxies for our groups is less than half that for the groups of Geller and Huchra, while the mass-to-luminosity ratio is smaller, on the average, by more than an order of magnitude in our case. Geller-Huchra groups with mass-to-luminosity ratios greater than 1000 are most likely unreal.