Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < z < 3 selected by high star-formation rate

¹ Institut d’Astrophysique Spatiale, Univ. Paris-Sud, CNRS, Univ. Paris-Saclay, Univ. Paris-Sud, bât. 121, Orsay Cedex 91405, France
² Department of Astronomy, Universidad de Concepción, Concepción Casilla 160-C, Chile
e-mail: cmartinache@astro-udec.cl
³ IPAC, Caltech, KS 314-6, Pasadena, CA 91125, USA
⁴ Sorbonne Université, CNRS UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, Paris 75014, France
⁵ Department of Astronomy/Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA
⁶ Herschel Science Centre, European Space Astronomy Centre, ESA, Villanueva de la Cañada, 28691, Spain
⁷ Aix-Marseille Univ., CNRS, Laboratoire d’Astrophysique de Marseille, Marseille, 13013, France
⁸ IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, 91191, France
⁹ Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, Gif-sur-Yvette, 91191, France
¹⁰ IRAP (Institut de Recherche en Astrophysique et Planétologie), Université de Toulouse, CNRS, UPS, Toulouse, France
¹¹ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza de San Juan 1 Planta-2, Teruel 44001, Spain
¹² INAF–Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, Via Bassini 15, Milano 20133, Italy
¹³ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
¹⁴ Sub-Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH, UK

Received: 9 April 2018
Accepted: 28 June 2018

Abstract

There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < z_p < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.