STATISTICAL DETERMINATION OF LINE-OF-SIGHT VELOCITY MEMBERSHIP OF GALAXY CLUSTERS

On the basis of a reasonable mathematical model, an improved approach for the statistical determination of line-of-sight velocity membership of galaxy clusters is developed, where the maximum likelihood method is used to solve the distribution parameters of the cluster, and then membership probabilities of individual galaxies in the cluster region can be quantitatively calculated. It is shown from detailed membership studies of the Coma cluster and the Virgo cluster that the approach i s not only theoretically rigorous but also practically feasible, from which effective discrimination between cluster members and field galax ies in a cluster region can be made very successfully. Furthermore the results of membership determination gained from the approach are in g ood agreement with what the dynamical model of galaxy clusters require s.