Distant clusters of galaxies in a deep XMM-Newton observation

The XMM-Newton Distant Cluster Project (XDCP) aims at the identification of a well defined sample of X-ray selected clusters of galaxies at redshifts z ≥ 0.8. As part of this project, we analyse the deep archival XMM-Newton exposure of LBQS 2212–1759 to quantify the cluster content. We validate the optical follow-up strategy as well as the X-ray selection function. We base the cluster identification of the extended X-ray sources on deep imaging with the ESO-VLT and on the CFHT-LS. The confirmation of cluster candidates is done by VLT/FORS2 spectroscopy. Photometric redshifts from CFTH-LS D4 are utilised to confirm the effectiveness of the X-ray cluster selection method. The survey sensitivity is computed to have a flux limit of S0.5–2.0 keV ∼ 2.5×10–15 erg s–1 for 50% completeness in an area ∼0.13 deg2. We detect six clusters of galaxies above this level both in X-rays and the optical. Two newly discovered X-ray luminous clusters of galaxies in this work are at z ≥ 1.0 and one is at z = 0.41. The constructed log N -log S tends to favour a scenario where no evolution in the cluster X-ray luminosity function takes place. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)