The tree clustering technique and the physical reality of galaxy groups

In this paper the tree clustering technique (the Euclidean separation distance coefficients) is suggested to test how the Hickson compact groups of galaxies (HCGs) are really physical groups. The method is applied on groups of 5 members only in Hickson's catalog. a 2013 Production and hosting by Elsevier B.V. on behalf of National Research Institute of Astronomy and Geophysics.