Spectroscopic characterization of galaxy clusters in RCS-1: Spectroscopic confirmation, redshift accuracy, and dynamical mass-richness relation

David G. Gilbank, L. Felipe Barrientos, Erica Ellingson, Kris Blindert, H. K.C. Yee, T. Anguita, M. D. Gladders, P. B. Hall, G. Hertling, L. Infante, R. Yan, M. Carrasco, Cristina Garcia-Vergara, K. S. Dawson, C. Lidman, T. Morokuma

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We present follow-up spectroscopic observations of galaxy clusters from the first Red-sequence Cluster Survey (RCS-1). This work focuses on two samples, a lower redshift sample of ~30 clusters ranging in redshift from z~0.2-0.6 observedwith multiobject spectroscopy (MOS) on 4-6.5-m class telescopes and a z ~ 1 sample of ~10 clusters 8-m class telescope observations. We examine the detection efficiency and redshift accuracy of the now widely used redsequence technique for selecting clusters via overdensities of red-sequence galaxies. Using both these data and extended samples including previously published RCS-1 spectroscopy and spectroscopic redshifts from SDSS, we find that the red-sequence redshift using simple twofilter cluster photometric redshifts is accurate to σz ≈ 0.035(1 + z) in RCS-1. This accuracy can potentially be improved with better survey photometric calibration. For the lower redshift sample, ~5 per cent of clusters show some (minor) contamination from secondary systems with the same red-sequence intruding into the measurement aperture of the original cluster. At z ~ 1, the rate rises to ~20 per cent. Approximately ten per cent of projections are expected to be serious, where the two components contribute significant numbers of their red-sequence galaxies to another cluster. Finally, we present a preliminary study of the mass-richness calibration using velocity dispersions to probe the dynamical masses of the clusters. We find a relation broadly consistent with that seen in the local universe from the WINGS sample at z ~ 0.05.

Original languageEnglish
Pages (from-to)1991-2012
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - May 11 2018

Bibliographical note

Funding Information:
DGG acknowledges support from the National Research Foundation of South Africa. Support for LFB and TA is provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. LI and LFB are in part supported by CONICYT-Chile grant Basal-CATA PFB-06/2007. HKCYacknowledge support for this project from a Discovery Grant from the National Science and Engineering Research Council of Canada and grants from the Canada Research Chair Program. MC's research is supported by the Transregional Collaborative Research Centre TRR 33. This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. This paper also includes data based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

Publisher Copyright:
© 2018 The Author(s).


  • Galaxies: clusters: general
  • Galaxies: distances and redshifts

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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