A low-mass galaxy cluster as a test-case study for the NIKA2 SZ Large Program

¹ Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 53, avenue des Martyrs, 38000 Grenoble, France
² LLR (Laboratoire Leprince-Ringuet), CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
³ Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan, 1, planta 2, E-44001, Teruel, Spain
⁴ Astronomy Instrumentation Group, University of Cardiff, UK
⁵ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
⁶ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁷ Institut d’Astrophysique Spatiale (IAS), CNRS and Université Paris Sud, Orsay, France
⁸ Institut Néel, CNRS and Université Grenoble Alpes, France
⁹ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy
¹⁰ Institut de RadioAstronomie Millimétrique (IRAM), Grenoble, France
¹¹ Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, 28850 Madrid, Spain
¹² Instituto de Radioastronomía Milimétrica (IRAM), Granada, Spain
¹³ Aix Marseille Univ, CNRS, CNES, LAM (Laboratoire d’Astrophysique de Marseille), Marseille, France
¹⁴ LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMCUniv. Paris 06, 75014 Paris, France
¹⁵ School of Earth and Space Exploration and Department of Physics, Arizona State University, Tempe, AZ 85287
¹⁶ IRAP, Université de Toulouse, CNRS, CNES, UPS, (Toulouse), France
¹⁷ Institut d’Astrophysique de Paris, CNRS (UMR7095), 98 bis boulevard Arago, 75014 Paris, France
¹⁸ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

^* e-mail: keruzore@lpsc.in2p3.fr

Published online: 27 January 2020

Abstract

High-resolution mapping of the hot gas in galaxy clusters is a key tool for cluster-based cosmological analyses. Taking advantage of the NIKA2 millimeter camera operated at the IRAM 30-m telescope, the NIKA2 SZ Large Program seeks to get a high-resolution follow-up of 45 galaxy clusters covering a wide mass range at high redshift in order to re-calibrate some of the tools needed for the cosmological exploitation of SZ surveys. We present the second cluster analysis of this program, targeting one of the faintest sources of the sample in order to tackle the difficulties in data reduction for such faint, low-SNR clusters. In this study, the main challenge is the precise estimation of the contamination by sub-millimetric point sources, which greatly affects the tSZ map of the cluster. We account for this contamination by performing a joint fit of the SZ signal and of the flux density of the compact sources. A prior knowledge of these fluxes is given by the adjustment of the SED of each source using data from both NIKA2 and the Herschel satellite. The first results are very promising and demonstrate the possibility to estimate thermodynamic properties with NIKA2, even in a compact cluster heavily contaminated by point sources.