The luminosity-temperature relation at z=0.4 for clusters of galaxies

We have obtained the first large sample of accurate temperatures for clusters at z > 0.14 from ASCA. We compare the luminosity-temperature (L-T) distribution for these clusters with the low-redshift sample of David and coworkers and find that there is no evidence for evolution. We also find that the intrinsic variance in this relation is roughly constant with redshift. Additionally, there is no detectable change in the relationship of optical velocity dispersion to X-ray temperature with redshift. Most cosmological simulations driven primarily by gravity predict substantial changes in the L-T relation due to the recent rapid growth of clusters. Our results are consistent either with models in which the cluster core entropy is dominated by preheating, or with low-Omega models in which cluster structure does not evolve strongly with time. The intrinsic variance in the L-T relation at a fixed redshift can be due to variety of possible causes, e.g., a change in the baryonic fraction from cluster to cluster, variation in the fraction of the total energy in the system arising from shocks or supernova heating, or variations in the emission measure distributions in multiphase gas.