The XMM Cluster Survey: a massive galaxy cluster at z = 1.45

S. A. Stanford, A. Kathy Romer, Kivanc Sabirli, Michael Davidson, Matt Hilton, Pedro T. P. Viana, Chris A. Collins, Scott T. Kay, Andrew R. Liddle, Robert G. Mann, Christopher J. Miller, Robert C. Nichol, Michael J. West, Christopher J. Conselice, Hyron Spinrad, Daniel Stern, Kevin Bundy

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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.
Original languageEnglish
Pages (from-to)L13-L16
JournalThe Astrophysical Journal
Issue number1
Early online date14 Jul 2006
Publication statusPublished - 20 Jul 2006


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