SEARCHING FOR ROTATING GALAXY CLUSTERS IN SDSS AND 2dFGRS

摘要

We present the results of a search for galaxy clusters that show an indication of global rotation using a spectroscopic sample of galaxies in SDSS and 2dFGRS. We have determined the member galaxies of 899 Abell clusters covered by these surveys using the galaxies' redshift and positional data and have estimated the ratio of the cluster rotation amplitude to the cluster velocity dispersion and the velocity gradient across the cluster. We found 12 tentative rotating clusters with large ratios of rotation amplitude to dispersion and large velocity gradients. We determine the morphological parameters for these 12 clusters using the positional information on the member galaxies: the ellipticity of the dispersion ellipse is in the range 0.08-0.57, and the position angle of its major and minor axes does not appear to be related to that of the rotation axis. We investigate the substructures in the sample of tentative rotating clusters, finding from Dressler-Shectman plots that the majority (9 out of 12) show evidence of substructure due to spatially correlated galaxy velocities. We have selected six probable rotating clusters (Abell 954, 1139, 1399, 2162, 2169, and 2366) that show a single number-density peak around the cluster center with a spatial segregation of high- and low-velocity galaxies. We find no strong evidence of recent mergers for the probable rotating clusters: they do not deviate significantly from the relation between X-ray luminosity and the velocity dispersion or virial mass of the clusters, and in two (Abell 954 and Abell 1399), the brightest cluster galaxies have small values of peculiar velocity and clustercentric distance.