The evolution of the cluster X - ray scaling relations in the WARPS sample at 0 . 6 < z

The X-ray properties of a sample of 11 high-redshift (0.6 < z < 1.0) clusters observed with Chandra and/or XMM-Newton are used to investigate the evolution of the cluster scaling relations. The observed evolution in the normalisation of the L− T, M− T, Mg − T, and M− L relations are consistent with simple self-similar predictions, in which the properties of clusters reflect the properties of the universe at their redshift of observation. Under the assumption that the model of self-similar evolution is correct and that the local systems formed via a single spherical collapse, the high-redshift L− T relation is consistent with the high-z clusters having virialised at a significantly higher redshift than the local systems. The data are also consistent with the more realistic scenario of clusters forming via the continuous accretion of material. The slope of the L− T relation at high-redshift (B = 3.32 ± 0.37) is consistent with the local relation, and significantly steeper then the self-similar prediction of B = 2. This suggests that the same non-gravitational processes are responsible for steepening the local and high-z relations, possibly occurring universally at z >∼ 1 or in the early stages of the clusters’ formation, prior to their observation. The properties of the intra-cluster medium at high-redshift are found to be similar to those in the local universe. The mean surface-brightness profile slope for the sample is β = 0.66±0.05, the mean gas mass fractions within R2500(z) and R200(z) are 0.069± 0.012 and 0.11 ± 0.02 respectively, and the mean metallicity of the sample is 0.28 ± 0.11Z⊙.