We present new spectroscopic observations of the most distant X-ray selected galaxy cluster currently known , XMMXCS J2215.9 - 1738 at z = 1.457 , obtained with the DEIMOS instrument at the W. M. Keck Observatory , and the FORS2 instrument on the ESO Very Large Telescope .
Within the cluster virial radius , as estimated from the cluster X-ray properties , we increase the number of known spectroscopic cluster members to 17 objects , and calculate the line of sight velocity dispersion of the cluster to be 580 \pm 140 km s ^ { -1 } .
We find mild evidence that the velocity distribution of galaxies within the virial radius deviates from a single Gaussian .
We show that the properties of J2215.9 - 1738 are inconsistent with self-similar evolution of local X-ray scaling relations , finding that the cluster is underluminous given its X-ray temperature , and that the intracluster medium contains \sim 2 - 3 times the kinetic energy per unit mass of the cluster galaxies .
These results can perhaps be explained if the cluster is observed in the aftermath of an off-axis merger .
Alternatively , heating of the intracluster medium through supernovae and/or Active Galactic Nuclei activity , as is required to explain the observed slope of the local X-ray luminosity–temperature relation , may be responsible .