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

• Published in: The Astrophysical Journal
• Main Authors: 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., Desai, S., Dobbs, M. A., Dudley, J. P., Fazio, G. G., Forman, W. R., Garmire, G., George, E. M., Gladders, M. D., Gonzalez, A. H., Halverson, N. W., High, F. W., Holder, G. P., Holzapfel, W. L., Hoover, S., Hrubes, J. D., Jones, C., Joy, M., Keisler, R., Knox, L., Lee, A. T., Leitch, E. M., Lueker, M., Luong-Van, D., Marrone, D. P., McMahon, J. J., Mehl, J., Meyer, S. S., Mohr, J. J., Montroy, T. E., Murray, S. S., Padin, S., Plagge, T., Pryke, C., Reichardt, C. L., Rest, A., Ruhl, J. E., Saliwanchik, B. R., Saro, A., Schaffer, K. K., Shaw, L., Shirokoff, E., Song, J., Spieler, H. G., Stalder, B., Stanford, S. A., Staniszewski, Z., Stark, A. A., Story, K., Stubbs, C. W., Vanderlinde, K., Vieira, J. D., Vikhlinin, A., Williamson, R., Zenteno, A.
• Other Authors: Mcmahon, J. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: early universe; galaxies: clusters: individual (SPT-CL J2106-5844); galaxies: evolution; galaxies: formation; large-scale structure of universe; Astronomy and Astrophysic; Space and Planetary Science; South Pole; South pole
• Online Access: http://hdl.handle.net/11368/2963119; https://doi.org/10.1088/0004-637X/731/2/86; http://iopscience.iop.org/0004-637X/731/2/86/pdf/0004-637X_731_2_86.pdf

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 −1.9 keV and a luminosity (within r500) of LX(0.5–2.0 keV) = (13.9±1.0)×1044 erg s−1. The combined mass estimate from measurements of the SZ effect and X-ray data is M200 = (1.27±0.21)×1015 h−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 2500 deg2 SPT survey region and that only one such galaxy cluster is expected in the entire sky.