Program: GN-2012B-Q-72

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 use GMOS spectroscopic observations to measure the velocity dispersions of a sample of z > 0.5 X-ray selected clusters drawn from the XMM Cluster Survey. This will provide a mass proxy that is independent of the cluster gas properties. Ultimately we aim to build the largest sample of z > 0.5 clusters with high quality X-ray luminosity, temperature, and dynamical mass measurements. In combination with the well-defined selection function of the sample, this will provide the most comprehensive view of X-ray scaling relation evolution yet, and provide valuable input into the mass calibration of cosmological cluster surveys at other wavelengths. This is the final request required to complete ongoing programs using both GMOS instruments in 2011B/2012A, and will bring the sample to a total of 20 objects.