PI: Felipe Menanteau, University of Illinois, email@example.com
Address: National Center for Supercomputing Applications, 1205 W. Clark St., Urbana, IL 61801, USA
CoI: John P. Hughes, Rutgers University
CoI: Felipe Barrientos, P. Universidad Catolica de Chile
CoI: Leopoldo Infante, P. Universidad Catolica de Chile
Title: Is ``El Gordo'' the fattest cluster 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) catalog, which contains 130 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~1.5. Preliminary results from our 2014A observations (10 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~ 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 (like ``El Gordo''). 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.