* Astronomy

Title: SPT-CL J0205-5829: A z = 1.32 evolved massive galaxy cluster in the south pole telescope Sunyaev-Zel'dovich effect survey
Authors: B. Stalder, J. Ruel, R. Suhada, M. Brodwin, K. A. Aird, K. Andersson, R. Armstrong, M. L. N. Ashby, M. Bautz, M. Bayliss, G. Bazin, B. A. Benson, L. E. Bleem, J. E. Carlstrom, C. L. Chang, H. M. Cho, A. Clocchiatti, T. M. Crawford, A. T. Crites, T. de Haan, S. Desai, M. A. Dobbs, J. P. Dudley, R. J. Foley, W. R. Forman, E. M. George, D. Gettings, M. D. Gladders, A. H. Gonzalez, N. W. Halverson, N. L. Harrington, 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, J. Liu, M. Lueker, D. Luong-Van, A. Mantz, D. P. Marrone, M. McDonald, J. J. McMahon, J. Mehl, S. S. Meyer, L. Mocanu, J. J. Mohr, T. E. Montroy, S. S. Murray, T. Natoli, D. Nurgaliev, S. Padin, T. Plagge, C. Pryke, C. L. Reichardt, A. Rest, J. E. Ruhl, et al. (20 additional authors not shown)

The galaxy cluster SPT-CL J0205-5829 currently has the highest spectroscopically-confirmed redshift, z=1.322, in the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. XMM-Newton observations measure a core-excluded temperature of Tx=8.7keV producing a mass estimate that is consistent with the Sunyaev-Zel'dovich derived mass. The combined SZ and X-ray mass estimate of M500=(4.9±0.8)e14 h_{70}^{-1} solar masses makes it the most massive known galaxy cluster at z>1.2 and the second most massive at z>1. Using optical and infrared observations, we find that SPT-CL J0205-5829 already had a strong red sequence of passive galaxies by the time the universe was <5 Gyr old, with stellar population ages >3 Gyr, and low rates of star formation (<0.5 solar masses/yr) in the central galaxies. We find that, despite the high redshift and mass, the existence of SPT-CL J0205-5829 is not surprising given a flat LambdaCDM cosmology with Gaussian initial perturbations. The a priori chance of finding a cluster of similar rarity (or rarer) in a survey the size of the 2500 deg² SPT-SZ survey is 69%.

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