GIOIA I.M., HENRY J.P., MULLIS C.R., VOGES W., BRIEL U.G., BOHRINGER H. and HUCHRA J.P.
Abstract (from CDS):
The deepest region of the ROSAT All-Sky Survey, at the north ecliptic pole, has been studied to produce a complete and unbiased X-ray-selected sample of clusters of galaxies. This sample is used to investigate the nature of cluster evolution and to explore the potential implications for large-scale structure models. The survey is 99.6% optically identified. Spectroscopic redshifts have been measured for all the extragalactic identifications. In this Letter, first results on cluster evolution are presented based on a comparison between the number of the observed clusters in the north ecliptic pole survey and the number of expected clusters assuming no-evolution models. At z>0.3, there is a deficit of clusters with respect to the local universe that is significant at greater than 4.7σ. The evolution appears to commence at L0.5–2.0keV>1.8x1044 ergs.s–1 in our data. The negative evolution goes in the same direction as the original Extended Medium-Sensitivity Survey result, the results from the 160 deg2 survey, and the recent results from the ROSAT Deep Cluster Survey. At lower redshifts, there is no evidence for evolution, a result in agreement with these and other cluster surveys.
Galaxies: Clusters: General - Surveys - X-Rays: Galaxies - X-Rays: General