EVOLUTION OF CLUSTER X-RAY LUMINOSITIES AND RADII - RESULTS FROM THE 160 SQUARE DEGREE ROSAT SURVEY

We searched for cluster X-ray luminosity and radius evolution using ou r sample of 203 galaxy clusters detected in the 160 deg(2) survey with the ROSAT PSPC (Vikhlinin et al.). With such a large area survey, it is possible, for the first time with ROSAT, to test the evolution of l uminous clusters, L-X > 3 x 10(44) ergs s(-1) in the 0.5-2 keV band. W e detect a factor of 3-4 deficit of such luminous clusters at z > 0.3 compared with the present. The evolution is much weaker or absent at m odestly lower luminosities, (1-3) x 10(44) ergs s(-1). At still lower luminosities, we find no evolution from the analysis of the log N-log S relation. The results in the two upper L, bins are in agreement with the Einstein Extended Medium-Sensitivity Survey evolution result (Gio ia et al.; Henry ct al.), which was obtained using a completely indepe ndent cluster sample. The low-L-X results are in agreement with other ROSAT surveys (e.g., Rosati et al.; Jones et al.). We also compare the distribution of core radii of nearby and distant (z > 0.4) luminous ( with equivalent temperatures of 4-7 keV) clusters and detect no evolut ion. The ratio of average core radius for z similar to 0.5 and z < 0.1 clusters is 0.9 +/- 0.1, and the core radius distributions are remark ably similar. A decrease of cluster sizes incompatible with our data i s predicted by self-similar evolution models for a high-Omega universe .