The XMM Cluster Survey: evolution of the velocity dispersion --
  temperature relation over half a Hubble time
  We measure the evolution of the velocity dispersion--temperature
($\sigma_{\rm v}$--$T_{\rm X}$) relation up to $z = 1$ using a sample of 38
galaxy clusters drawn from the \textit{XMM} Cluster Survey. This work improves
upon previous studies by the use of a homogeneous cluster sample and in terms
of the number of high redshift clusters included. We present here new redshift
and velocity dispersion measurements for 12 $z > 0.5$ clusters observed with
the GMOS instruments on the Gemini telescopes. Using an orthogonal regression
method, we find that the slope of the relation is steeper than that expected if
clusters were self-similar, and that the evolution of the normalisation is
slightly negative, but not significantly different from zero ($\sigma_{\rm v}
\propto T^{0.86 \pm 0.14} E(z)^{-0.37 \pm 0.33}$). We verify our results by
applying our methods to cosmological hydrodynamical simulations. The lack of
evolution seen in our data is consistent with simulations that include both
feedback and radiative cooling.
