Discovery and cosmological implications of SPT-CL J2106-5844, the most massive known cluster at z>1

R. J. Foley, K. Andersson, G. Bazin, T. De Haan, J. Ruel, P. A R Ade, K. A. Aird, R. Armstrong, M. L N Ashby, M. Bautz, B. A. Benson, L. E. Bleem, M. Bonamente, M. Brodwin, J. E. Carlstrom, C. L. Chang, A. Clocchiatti, T. M. Crawford, A. T. Crites, S. DesaiM. A. Dobbs, J. P. Dudley, G. G. Fazio, W. R. Forman, G. Garmire, E. M. George, M. D. Gladders, A. H. Gonzalez, N. W. Halverson, F. W. High, G. P. Holder, W. L. Holzapfel, S. Hoover, J. D. Hrubes, C. Jones, M. Joy, R. Keisler, L. Knox, A. T. Lee, E. M. Leitch, M. Lueker, D. Luong-Van, D. P. Marrone, J. J. McMahon, J. Mehl, S. S. Meyer, J. J. Mohr, T. E. Montroy, S. S. Murray, S. Padin, T. Plagge, C. Pryke, C. L. Reichardt, A. Rest, J. E. Ruhl, B. R. Saliwanchik, A. Saro, K. K. Schaffer, L. Shaw, E. Shirokoff, J. Song, H. G. Spieler, B. Stalder, S. A. Stanford, Z. Staniszewski, A. A. Stark, K. Story, C. W. Stubbs, K. Vanderlinde, J. D. Vieira, A. Vikhlinin, R. Williamson, A. Zenteno

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112 Scopus citations


Using the South Pole Telescope (SPT), we have discovered the most massive known galaxy cluster at z>1, SPT-CL J2106-5844. In addition to producing a strong Sunyaev-Zel'dovich (SZ) effect signal, this system is a luminous X-ray source and its numerous constituent galaxies display spatial and color clustering, all indicating the presence of a massive galaxy cluster. Very Large Telescope and Magellan spectroscopy of 18 member galaxies shows that the cluster is at z = 1.132+0.002 -0.003. Chandra observations obtained through a combined HRC-ACIS GTO program reveal an X-ray spectrum with an Fe K line redshifted by z = 1.18 ± 0.03. These redshifts are consistent with the galaxy colors found in optical, near-infrared, and mid-infrared imaging. SPT-CL J2106-5844 displays extreme X-ray properties for a cluster having a core-excluded temperature of TX = 11.0 +2.6 -1.9keV and a luminosity (within r 500) of LX (0.5-2.0 keV) = (13.9 ± 1.0) × 10 44ergs-1. The combined mass estimate from measurements of the SZ effect and X-ray data is M 200 = (1.27 ± 0.21) × 1015h -1 70 M . The discovery of such a massive gravitationally collapsed system at high redshift provides an interesting laboratory for galaxy formation and evolution, and is a probe of extreme perturbations of the primordial matter density field. We discuss the latter, determining that, under the assumption of ΛCDM cosmology with only Gaussian perturbations, there is only a 7% chance of finding a galaxy cluster similar to SPT-CL J2106-5844 in the 2500deg2 SPT survey region and that only one such galaxy cluster is expected in the entire sky.

Original languageEnglish (US)
Article number86
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 20 2011


  • early universe
  • galaxies: clusters: individual (SPT-CL J2106-5844)
  • galaxies: evolution
  • galaxies: formation
  • large-scale structure of universe


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