THE LUMINOSITY FUNCTION OF CLUSTER GALAXIES - RELATIONS AMONG M(1), M-ASTERISK AND THE MORPHOLOGICAL TYPE

A study of the luminosity function of 36 Abell clusters of galaxies ha s been carried out using photographic plates obtained with the Palomar 1.2 m Schmidt telescope. The relation between the magnitude M(1) of t he brightest cluster member and the Schechter function parameter M ha s been analyzed. A positive correlation between M and M(1) is found. However clusters appear segregated in the M(1)-M plane according to t heir Rood & Sastry class in such a way that on average M(1) becomes br ighter while M becomes fainter going from late to early Rood & Sastry and also Bautz & Morgan classes. Also a partial correlation analysis involving the magnitude M(10) of the 10th brightest galaxy, shows a ne gative intrinsic correlation between M(1) and M. These results agree with the cannibalism model for the formation of brightest cluster memb ers, and provide new constraints for theories of cluster formation and evolution.