Program: GS-2009B-Q-80

The observed evolution of X-ray cluster scaling relations provides a powerful method of discriminating between different models of heating by AGN and/or supernovae ('feedback') within clusters. Understanding the evolution of the cluster physics is not only essential for enabling clusters to provide precision measurements of cosmological parameters, but also places constraints on models of galaxy formation and evolution, in which feedback is now an essential ingredient. We propose to obtain spectroscopic redshifts of 10 clusters selected from the XMM Cluster Survey, detected with enough X-ray counts to facillitate temperature measurements, and estimated to lie at redshift ~0.7. This will provide the largest such sample to date at this redshift, an epoch where different model predictions diverge significantly. In combination with the complete lower redshift XCS cluster sample with its well defined selection function, the GMOS observations will help to produce the most comprehensive view of X-ray scaling relation evolution yet.