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Published December 20, 2014 | Submitted + Published
Journal Article Open

Candidate Clusters of Galaxies at z > 1.3 Identified in the Spitzer South Pole Telescope Deep Field Survey


We present 279 galaxy cluster candidates at z > 1.3 selected from the 94 deg^2 Spitzer South Pole Telescope Deep Field (SSDF) survey. We use a simple algorithm to select candidate high-redshift clusters of galaxies based on Spitzer/IRAC mid-infrared data combined with shallow all-sky optical data. We identify distant cluster candidates adopting an overdensity threshold that results in a high purity (80%) cluster sample based on tests in the Spitzer Deep, Wide-Field Survey of the Boötes field. Our simple algorithm detects all three 1.4 < z ≤ 1.75 X-ray detected clusters in the Boötes field. The uniqueness of the SSDF survey resides not just in its area, one of the largest contiguous extragalactic fields observed with Spitzer, but also in its deep, multi-wavelength coverage by the South Pole Telescope (SPT), Herschel/SPIRE, and XMM-Newton. This rich data set will allow direct or stacked measurements of Sunyaev-Zel'dovich effect decrements or X-ray masses for many of the SSDF clusters presented here, and enable a systematic study of the most distant clusters on an unprecedented scale. We measure the angular correlation function of our sample and find that these candidates show strong clustering. Employing the COSMOS/UltraVista photometric catalog in order to infer the redshift distribution of our cluster selection, we find that these clusters have a comoving number density N_c = (0.7^(+6.3)_(0.6)) x 10^(-7) h^3 Mpc^(-3) and a spatial clustering correlation scale length r_ 0 = (32 ± 7) h^(–1) Mpc. Assuming our sample is comprised of dark matter halos above a characteristic minimum mass, M _(min), we derive that at z = 1.5 these clusters reside in halos larger than M_(min) = 1.5^(+0.9)_(0.7) x 10^(14) h^(-1) M_⊙. We find that the mean mass of our cluster sample is equal to M_(mean) = 1.9^(+1.0)_(0.8) x 10^(14) h^(-1) M_⊙ ; thus, our sample contains the progenitors of present-day massive galaxy clusters.

Additional Information

© 2014 The American Astronomical Society. Received 2014 March 20; Accepted 2014 October 14; Published 2014 December 5. A.R. is grateful to the SSDF Team for providing access to advanced data products and is thankful to Audrey Galametz, Dominika Wylezalek, Loredana Vetere, and Roberto Assef for useful discussions and comments on this paper. This work is based on data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Lab (JPL), California Institute of Technology (Caltech), under a contract with NASA. Support was provided by NASA through contract number 1439211 issued by JPL/Caltech. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. Facilities: Spitzer, UKST

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Published - 0004-637X_797_2_109.pdf

Submitted - 1404.0023v1.pdf


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