2002AJ....124...33H

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 β=0.49±0.06 and r_core=165±5 kpc (Ω_m=0.3, Ω_Λ=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^+1.5_–0.9 keV and a bolometric luminosity of 8.2^+1.7_–1.6x10⁴³ ergs.s^–1 for RDCS 1317+2911, and a temperature of 4.9^+1.3_–0.9 keV and a bolometric luminosity of 4.1^+0.5_–0.4x10⁴⁴ 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 β 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 z_median=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)^α, we find α=2.9±0.4, L₆=8.7±0.9x10⁴⁴ 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 σ 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.