SPT-CL J2040-4451: An SZ-selected galaxy cluster at z = 1.478 with significant ongoing star formation

M. B. Bayliss, M. L.N. Ashby, J. Ruel, M. Brodwin, K. A. Aird, M. W. Bautz, B. A. Benson, L. E. Bleem, S. Bocquet, J. E. Carlstrom, C. L. Chang, H. M. Cho, A. Clocchiatti, T. M. Crawford, A. T. Crites, S. Desai, M. A. Dobbs, J. P. Dudley, Ryan Joseph Foley, W. R. FormanE. M. George, D. Gettings, M. D. Gladders, A. H. Gonzalez, T. De Haan, 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, J. Liu, M. Lueker, D. Luong-Van, A. Mantz, D. P. Marrone, K. Mawatari, M. McDonald, J. J. McMahon, J. Mehl, S. S. Meyer, E. D. Miller, L. Mocanu, 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, J. T. Sayre, K. K. Schaffer, E. Shirokoff, J. Song, B. Stalder, R. Šuhada, H. G. Spieler, S. A. Stanford, Z. Staniszewski, A. A. Stark, K. Story, C. W. Stubbs, A. Van Engelen, K. Vanderlinde, J. D. Vieira, A. Vikhlinin, R. Williamson, O. Zahn, A. Zenteno

Research output: Contribution to journalArticlepeer-review


SPT-CL J2040-4451 - spectroscopically confirmed at z = 1.478 - is the highest-redshift galaxy cluster yet discovered via the Sunyaev-Zel'dovich effect. SPT-CL J2040-4451 was a candidate galaxy cluster identified in the first 720 deg2of the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey, and has been confirmed in follow-up imaging and spectroscopy. From multi-object spectroscopy with Magellan-I/Baade+IMACS we measure spectroscopic redshifts for 15 cluster member galaxies, all of which have strong [O II] λλ3727 emission. SPT-CL J2040-4451 has an SZ-measured mass of M500, SZ = 3.2 ± 0.8 × 1014Mh, corresponding to M200, SZ = 5.8 ± 1.4 × 1014Mh. The velocity dispersion measured entirely from blue star-forming members is σv= 1500 ± 520 km s-1. The prevalence of star-forming cluster members (galaxies with >1.5 M yr-1) implies that this massive, high-redshift cluster is experiencing a phase of active star formation, and supports recent results showing a marked increase in star formation occurring in galaxy clusters at z ≳ 1.4. We also compute the probability of finding a cluster as rare as this in the SPT-SZ survey to be >99%, indicating that its discovery is not in tension with the concordance ΛCDM cosmological model.

Original languageEnglish (US)
Article number12
JournalAstrophysical Journal
Issue number1
StatePublished - Oct 10 2014


  • galaxies: clusters: individual (SPT-CL J2040-4451)
  • galaxies: distances and redshifts
  • galaxies: evolution
  • large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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