The XMM Cluster Survey: evolution of the velocity dispersion -- temperature relation over half a Hubble time

TL;DR

This study investigates how the velocity dispersion--temperature relation of galaxy clusters evolves up to redshift 1, using a homogeneous sample and new high-redshift data, finding a steeper slope and little to no evolution in normalization.

Contribution

It provides new measurements of high-redshift cluster velocity dispersions and analyzes the evolution of the $\sigma_v$--$T_X$ relation with improved data and methods.

Findings

Steeper $\sigma_v$--$T_X$ relation than self-similar models

Normalization shows no significant evolution with redshift

Results consistent with simulations including feedback and cooling

Abstract

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.