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, Daniel 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

Research output: Contribution to journalArticle

93 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
Externally publishedYes



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

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Foley, R. J., Andersson, K., Bazin, G., De Haan, T., Ruel, J., Ade, P. A. R., Aird, K. A., Armstrong, R., Ashby, M. L. N., Bautz, M., Benson, B. A., Bleem, L. E., Bonamente, M., Brodwin, M., Carlstrom, J. E., Chang, C. L., Clocchiatti, A., Crawford, T. M., Crites, A. T., ... Zenteno, A. (2011). Discovery and cosmological implications of SPT-CL J2106-5844, the most massive known cluster at z>1. Astrophysical Journal, 731(2), [86].