Evolution of Cluster X-Ray Luminosities and Radii: Results from the 160 Square Degree [ITAL]ROSAT[/ITAL] Survey

We searched for cluster X-ray luminosity and radius evolution using oursample of 200 galaxy clusters detected in the 160 deg^2 survey with the ROSATPSPC (Vikhlinin et al. 1998, astro-ph/9803099). With such a large area survey,it is possible, for the first time with ROSAT, to test the evolution ofluminous clusters, Lx > 3x10^44 erg/s, in the 0.5-2 keV band. We detect afactor of 3-4 deficit of such luminous clusters at z>0.3 compared to thepresent. The evolution is much weaker or absent at modestly lower luminosities,1-3x10^44 erg/s. At still lower luminosities, we find no evolution from theanalysis of the log N - log S relation. The results in the two upper Lx binsare in agreement with the Einstein EMSS evolution result (Gioia et al. 1990a,Henry et al. 1992) while being obtained using a completely independent clustersample. The low-Lx results are in agreement with other ROSAT surveys (e.g.Rosati et al. 1998, Jones et al. 1998). We also compare the distribution of core radii of nearby and distant (z>0.4)luminous (with equivalent temperatures 4-7 keV) clusters, and detect noevolution. The ratio of average core radius for z~0.5 and z<0.1 clusters is0.9+/-0.1, and the core radius distributions are remarkably similar. A decreaseof cluster sizes incompatible with our data is predicted by self-similarevolution models for high-Omega universe.Comment: 5 pages including 3 ps figures, uses enclosed emulateapj.sty. ApJ Letters, in pres