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Redshifts, Sample Purity, and BCG Positions for the Galaxy Cluster Catalog from the First 720 Square Degrees of the South Pole Telescope Survey

Song, J. and Lueker, M. and Padin, S. and Shirokoff, E. and Vieira, J. D. (2012) Redshifts, Sample Purity, and BCG Positions for the Galaxy Cluster Catalog from the First 720 Square Degrees of the South Pole Telescope Survey. Astrophysical Journal, 761 (1). Art. No. 22. ISSN 0004-637X.

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We present the results of the ground- and space-based optical and near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with the Sunyaev-Zel'dovich (SZ) effect in the 720 deg^2 of the South Pole Telescope (SPT) survey completed in the 2008 and 2009 observing seasons. We use the optical/NIR data to establish whether each candidate is associated with an overdensity of galaxies and to estimate the cluster redshift. Most photometric redshifts are derived through a combination of three different cluster redshift estimators using red-sequence galaxies, resulting in an accuracy of Δz/(1 + z) = 0.017, determined through comparison with a subsample of 57 clusters for which we have spectroscopic redshifts. We successfully measure redshifts for 158 systems and present redshift lower limits for the remaining candidates. The redshift distribution of the confirmed clusters extends to z = 1.35 with a median of z_(med) = 0.57. Approximately 18% of the sample with measured redshifts lies at z > 0.8. We estimate a lower limit to the purity of this SPT SZ-selected sample by assuming that all unconfirmed clusters are noise fluctuations in the SPT data. We show that the cumulative purity at detection significance ξ > 5(ξ > 4.5) is ≥95% (≥70%). We present the red brightest cluster galaxy (rBCG) positions for the sample and examine the offsets between the SPT candidate position and the rBCG. The radial distribution of offsets is similar to that seen in X-ray-selected cluster samples, providing no evidence that SZ-selected cluster samples include a different fraction of recent mergers from X-ray-selected cluster samples.

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Additional Information:© 2012 American Astronomical Society. Received 2012 July 14; accepted 2012 October 16; published 2012 November 20. The South Pole Telescope program is supported by the National Science Foundation through grant ANT-0638937. Partial support is also provided by the NSF Physics Frontier Center grant PHY-0114422 to the Kavli Institute of Cosmological Physics at the University of Chicago, the Kavli Foundation, and the Gordon and Betty Moore Foundation. The Munich group acknowledges support from the Excellence Cluster Universe and the DFG research program TR33 The Dark Universe. Galaxy cluster research at Harvard is supported by NSF grant AST-1009012, and research at SAO is supported in part by NSF grants AST-1009649 and MRI-0723073. The McGill group acknowledges funding from the National Sciences and Engineering Research Council of Canada, Canada Research Chairs program, and the Canadian Institute for Advanced Research. Optical imaging data from the Blanco 4 m at Cerro Tololo Interamerican Observatories (programs 2005B-0043, 2009B-0400, 2010A-0441, 2010B-0598) and spectroscopic observations from VLT programs 086.A-0741 and 286.A-5021 and Gemini program GS-2009B-Q-16 were included in this work. Additional data were obtained with the 6.5 m Magellan Telescopes and the Swope telescope, which are located at the Las Campanas Observatory in Chile. This work is based in part on observations made with the Spitzer Space Telescope (PIDs 60099, 70053), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAGW-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. Facilities: Blanco (MOSAIC), Blanco (NEWFIRM), Gemini:South (GMOS), Magellan:Baade (IMACS), Magellan: Clay (LDSS3), SPT, Spitzer (IRAC), Swope, VLT:Antu (FORS2), WISE
Funding AgencyGrant Number
NSF Physics Frontier CenterPHY-0114422
Kavli FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Excellence Cluster UniverseUNSPECIFIED
DFG research program TR33 Dark UniverseUNSPECIFIED
National Sciences and Engineering Research Council of CanadaUNSPECIFIED
Canada Research Chairs programUNSPECIFIED
Canadian Institute for Advanced Research (CIAR)UNSPECIFIED
U.S. GovernmentNAGW-2166
Subject Keywords:cosmology: observations; galaxies: clusters: general; galaxies: distances and redshifts
Issue or Number:1
Record Number:CaltechAUTHORS:20130108-091715280
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Official Citation:Redshifts, Sample Purity, and BCG Positions for the Galaxy Cluster Catalog from the First 720 Square Degrees of the South Pole Telescope Survey J. Song et al. 2012 ApJ 761 22
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36228
Deposited By: Ruth Sustaita
Deposited On:08 Jan 2013 17:51
Last Modified:03 Oct 2019 04:36

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