Moderate-Temperature Clusters of Galaxies from the RDCS and the High-Redshift Luminosity-Temperature Relation

Abstract

We present our discovery observations and analysis of RDCS 1317+2911, z = 0.805, and RDCS 1350+6007, z = 0.804, two clusters of galaxies identified through X-ray emission in the ROSAT Deep Cluster Survey (RDCS). RDCS 1317+2911 has an unusual morphology in our Chandra observations, with an asymmetric surface brightness profile and a bend in the distribution of X-ray emission. In contrast, RDCS 1350+6007 appears to be more like low-redshift clusters, with ? = 0.49 ? 0.06 and rcore = 165 ? 5 kpc (?m = 0.3, ?? = 0.7, H0 = 65 km s-1 Mpc-1), though it also has an elliptical, slightly asymmetric surface brightness profile. We find a temperature of 3.7 keV and a bolometric luminosity of 8.2 ? 1043 ergs s-1 for RDCS 1317+2911, and a temperature of 4.9 keV and a bolometric luminosity of 4.1 ? 1044 ergs s-1 for RDCS 1350+6007. Our weak-lensing analysis of RDCS 1350+6007 confirms the general shape of the inner density profile but predicts twice the mass of the model based on the X-ray profile. There are two possibilities for this discrepancy: either there is a significant amount of mass near the redshift of the cluster that has not yet fallen into the potential well and shock-heated the gas, or, as we only see the X-ray emission from the core of the cluster, our ? model fails to describe the true shape of the underlying potential. We combine the X-ray luminosities and temperatures for RDCS clusters of galaxies with such measurements of other clusters at high redshift (z > 0.7) and fit the luminosity-temperature relation. We find no statistically significant evolution in the slope or zero point of this relation at zmedian = 0.83. This result is in agreement with models of intracluster medium evolution with significant preheating or high initial entropy values. Quantifying the bolometric luminosity-temperature relation as L = L6(1 + z)A(T/6 keV)?, we find ? = 2.9 ? 0.4, L6 = 8.7 ? 0.9 ? 1044 ergs s-1 and A = 0.3 ? 0.2, or A = 0.4 ? 0.2, depending on which low-redshift luminosity-temperature relation we compare with. With this result, we rule out at the 5 ? level the self-similar scaling model of intracluster medium evolution. We discuss how low-temperature, high-redshift clusters of galaxies will allow us to improve on this result, and we announce the discovery of two such objects, CXOU J0910.1+5419 and CXOU J1316.9+2914.