An X-ray underluminous cluster of galaxies in the 4Ms CDFS observations

Aims. We investigate the properties of cluster ClG 0332-2747 at z = 0.734 in the GOODS-South field, which was undetected in the Chandra 2Ms observations. We explore possible scenarios to explain the discrepancy between its low X-ray emission and that expected from the M − LX relation. Methods. We use the large public spectroscopic database available in the GOODS-South field to estimate the dynamical mass and the virialization status of ClG 0332-2747. Cluster members selected from their photometric redshift are used with spectroscopic ones to analyse the galaxy population of the cluster. In the newly released Chandra 4Ms observations we detect a faint extended X-ray emission associated to the cluster. Finally, we compare the optical and X-ray properties of ClG 0332-2747 with the predictions of a well-tested semianalytic model. Results. We estimate the velocity dispersion and the virial mass considering all 44 spectroscopic members, or 20 red-sequence members only. We obtain σv = 634 ± 105 km s −1 , M200 = 3.07 +1.57 −1.16 × 10