Photometric Properties of Low-redshift Galaxy Clusters

A comprehensive multicolor survey was undertaken to investigate global optical properties of Abell clusters of galaxies. This survey was christened the LowRedshift Cluster Optical Survey (LOCOS). LOCOS was devised to search for patterns of galaxy evolution induced by the environment. The generated data base contains accurate deep CCD photometric measurements (Kron-Cousins R, B and I) for a sample of 46 low-redshift (0.04 ≤ z ≤ 0.18) Abell clusters. This is one of the few large surveys that included the contribution due to dwarf galaxies (about 5.5 mag deeper than the R characteristic magnitude (M∗R); Ho = 50 h50kms −1 Mpc, qo = 0). Due to space restrictions only the main results concerning the variations at the bright-end of the luminosity function (LF) are presented here. Other results are presented elsewhere (López-Cruz & Yee 2000a,b). We have detected clear variations at both the bright end and the faint end of the LF. The nature of the variations at the bright end revealed that poor cD clusters have dimmer M∗R. We can explain these variations as a result of dynamical friction. On the other hand, non-cD clusters seem to have unaffected LFs. A third class termed as binary clusters seems to be a transition class that might have resulted from cluster-cluster mergers.