The X-ray size-temperature relation for intermediate-redshift galaxy clusters

We present the first measurements of the X-ray size-temperature (ST) relati on in intermediate-redshift (z similar to 0.30) galaxy clusters. We interpr et the local ST relation (z similar to 0.06) in terms of underlying scaling relations in the cluster dark matter properties, and then we use standard models for the redshift evolution of those dark matter properties to argue that the ST relation does not evolve with redshift. We then use ROSAT HRI o bservations of 11 clusters to examine the intermediate-redshift ST relation ; for currently favored cosmological parameters, the intermediate-redshift ST relation is consistent with that of local clusters. Finally, we use the ST relation and our evolution model to measure angular diameter distances; with these 11 distances we evaluate constraints on Omega (M) and Omega (Lam bda) that are consistent with those derived from studies of Type Ia superno vae. The data rule out a model with Omega (M) = 1 and Omega (Lambda) = 0 wi th 2.5 sigma confidence. When limited to models where Omega (M) + Omega (La mbda) = 1, these data are inconsistent with Omega (M) = 1 with 3 sigma conf idence.