The XMM Cluster Survey: A Massive Galaxy Cluster at z = 1.45

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

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 L_X = 4.4^(+0.8)_(-0.6) × 10^(44) ergs s^(-1) over a 2 Mpc radial region. The measured T_X, 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.

Additional Information

© 2006 American Astronomical Society. Received 2006 March 31; accepted 2006 June 5; published 2006 July 14. This work is based on data obtained by XMM-Newton, an ESA science mission funded by contributions from ESA member states and from NASA. We acknowledge financial support from the NASA-LTSA program, the RAS Hosie Bequest, Liverpool John Moores University, the Institute for Astronomy at the University of Edinburgh, the XMM and Chandra guest observer programs, Carnegie Mellon University, the NSF, and PPARC. This research made use of the NASA/IPAC Extragalactic Database, the SIMBAD facility at CDS, the NASA/ GSFC-supported XSPEC software, and the ESO Imaging Survey. The W. M. Keck Observatory is a scientific partnership between the University of California and the California Institute of Technology, made possible by a generous gift of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community; we are fortunate to have the opportunity to conduct observations from this mountain. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from NSF grant AST 00-71048. We thank the referee for helping to improve the final version of this paper. The work by S. A. S. at LLNL was performed under the auspices of the US Department of Energy under contract W-7405-ENG-48. The work of D. S. was carried out at the JPL, California Institute of Technology, under contract with NASA.

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