The XMM Cluster Survey: A Massive Galaxy Cluster at z = 1.45
Conselice, Christopher J.; Hilton, Matt; Stanford, S. A.; Spinrad, Hyron; Stern, Daniel; West, Michael J.; Romer, A. Kathy; Sabirli, Kivanc; Davidson, Michael; Viana, Pedro T. P.; Collins, Chris A.; Kay, Scott T.; Liddle, Andrew R.; Mann, Robert G.; Miller, Christopher J.; Nichol, Robert C.; Bundy, Kevin
United States, United Kingdom, Portugal, Chile
Abstract
We report the discovery of XMMXCS J2215.9-1738, a massive galaxy cluster at z=1.45, which was found in the XMM Cluster Survey. The cluster candidate was initially identified as an extended X-ray source in archival XMM data. Optical spectroscopy shows that six galaxies within a ~60" diameter region lie at z=1.45+/-0.01. Model fits to the X-ray spectra of the extended emission yield kT=7.4+2.7-1.8 keV (90% confidence); if there is an undetected central X-ray point source, then kT=6.5+2.6-1.8 keV. The bolometric X-ray luminosity is LX=4.4+0.8-0.6×1044 ergs s-1 over a 2 Mpc radial region. The measured TX, which is the highest for any known cluster at z>1, suggests that this cluster is relatively massive for such a high redshift. The redshift of XMMXCS J2215.9-1738 is the highest currently known for a spectroscopically confirmed cluster of galaxies.