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# Program Information for 2015B-0220

PI: John P Hughes, Rutgers U., jph@physics.rutgers.edu
Address: Department of Physics and Astronomy, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 USA

CoI: Felipe Menanteau, U. of Illinois Urbana-Champaign
CoI: Felipe Barrientos, Pontificia Universidad Catolica de Chile
CoI: Leopoldo Infante, Pontificia Universidad Catolica de Chile

Title: On the Trail of the Most Massive Galaxy Clusters in the Universe

Abstract: We propose to continue our program of optical and near-infrared (NIR) imaging to unveil {\em all} of the most massive clusters in the observable Universe. We start from the all-sky Planck Sunyaev- Zel'dovich (SZ) catalogs, which contain several hundred high significance (S/N$>5$) unconfirmed cluster candidates. Since SZ selection favors high mass clusters and the Planck confirmation process favored low redshift systems, the highest significance unconfirmed candidates are, therefore, likely massive clusters ($M_{500}> 5\times 10^{14}\, M_\odot$) at relatively high redshift ($z>0.5$). Our proposed observations, using the SOAR Optical Imager and Spartan IR Camera and MOSAIC and NEWFIRM on Mayall, are designed to confirm the presence of a brightest cluster galaxy and red sequence of accompanying cluster members to $z\sim1.5$. Preliminary results from our observations in 2014 (20 nights awarded on SOAR and Mayall) have validated our approach by the detection of optical clusters in a number of Planck candidates, including the discovery of a remarkably rich system at $z\sim 0.8$ that rivals the most massive clusters known. The proposed observations represent the first step required to provide a complete all-sky census throughout the observable Universe of the most massive, high redshift clusters. Their expected high redshift and high mass make the unconfirmed Planck clusters, arguably, the most important available sample for probing deviations from $\Lambda$CDM and defining the high- mass end of the cluster mass function.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 3 (2015B):  KP-4m/MOSA -- 2n on Oct 06 - Oct 07 2015
Run 4 (2015B):  KP-4m/NEWFIRM -- 2n on Nov 16 - Nov 17 2015

National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360

 NOAO >   Observing Info >   Approved Programs >   2015B-0220