DETECTING CLUSTERS IN GALAXY CATALOGS

A model of the procedure used by Abell to detect clusters in galaxy catalogs is presented. The model is used to calculate the signal-to-noise ratio for cluster detection in these catalogs. The results indicate that most of the Abell clusters out to z ∼ 0.1 probably do represent physical associations of galaxies but that the reliability of cluster detection at larger redshifts is poor. In addition, it is shown that the Abell selection criteria are not optimal. Various ways of optimizing the detection procedure are considered. In particular, it is shown that changing the magnitude range from m3 → m3 + 2 to m3 + 1 → m3 + 3 can significantly improve the signal-to-noise ratio.