Exploiting NIKA2/XMM-Newton imaging synergy for intermediate-mass high-z galaxy clusters within the NIKA2 SZ large program

Observations of ACT-CL J0215.4+0030 at z ∼ 0.9^⋆

¹ Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 53, Avenue des Martyrs, 38000 Grenoble, France
e-mail: keruzore@lpsc.in2p3.fr
² AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
³ LLR (Laboratoire Leprince-Ringuet), CNRS, École Polytechnique, Institut Polytechnique de Paris, Palaiseau, France
⁴ Astronomy Instrumentation Group, University of Cardiff, Cardiff, UK
⁵ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁶ Institut d’Astrophysique Spatiale (IAS), CNRS and Université Paris Sud, Orsay, France
⁷ Institut Néel, CNRS and Université Grenoble Alpes, Grenoble, France
⁸ Institut de RadioAstronomie Millimétrique (IRAM), Grenoble, France
⁹ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy
¹⁰ Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, 28850 Madrid, Spain
¹¹ Instituto de Radioastronomía Milimétrica (IRAM), Granada, Spain
¹² Aix Marseille Univ., CNRS, CNES, LAM (Laboratoire d’Astrophysique de Marseille), Marseille, France
¹³ Observatoire de Paris, PSL University, Sorbonne Université, CNRS, LERMA, 75014 Paris, France
¹⁴ School of Earth and Space Exploration and Department of Physics, Arizona State University, Tempe, AZ 85287, USA
¹⁵ IRAP, Université de Toulouse, CNRS, CNES, UPS, Toulouse, France
¹⁶ Département de Physique, Ecole Normale Supérieure, 24, Rue Lhomond, 75005 Paris, France
¹⁷ Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, USA
¹⁸ Institut d’Astrophysique de Paris, CNRS (UMR7095), 98 Bis boulevard Arago, 75014 Paris, France
¹⁹ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA

Received: 15 July 2020
Accepted: 5 October 2020

Abstract

High-resolution mapping of the intracluster medium (ICM) up to high redshift and down to low masses is crucial to derive accurate mass estimates of the galaxy cluster and to understand the systematic effects affecting cosmological studies based on galaxy clusters. We present a spatially resolved Sunyaev-Zel’dovich (SZ)/X-ray analysis of ACT-CL J0215.4+0030, a high-redshift (z = 0.865) galaxy cluster of intermediate mass (M₅₀₀ ≃ 3.5 × 10¹⁴ M_⊙) observed as part of the ongoing NIKA2 SZ large program, which is a follow-up of a representative sample of objects at 0.5 ≤ z ≤ 0.9. In addition to the faintness and small angular size induced by its mass and redshift, the cluster is contaminated by point sources that significantly affect the SZ signal. This is therefore an interesting case study for the most challenging sources of the NIKA2 cluster sample. We present the NIKA2 observations of this cluster and the resulting data. We identified the point sources that affect the NIKA2 maps of the cluster as submillimeter galaxies with counterparts in catalogs of sources constructed by the SPIRE instrument on board the Herschel observatory. We reconstructed the ICM pressure profile by performing a joint analysis of the SZ signal and of the point-source component in the NIKA2 150 GHz map. This cluster is a very weak source that lies below the selection limit of the Planck catalog. Nonetheless, we obtained high-quality estimates of the ICM thermodynamical properties with NIKA2. We compared the pressure profile extracted from the NIKA2 map to the pressure profile obtained from X-ray data alone by deprojecting the public XMM-Newton observations of the cluster. We combined the NIKA2 pressure profile with the X-ray deprojected density to extract detailed information on the ICM. The radial distribution of its thermodynamic properties (the pressure, temperature and entropy) indicate that the cluster has a highly disturbed core. We also computed the hydrostatic mass of the cluster, which is compatible with estimations from SZ and X-ray scaling relations. We conclude that the NIKA2 SZ large program can deliver quality information on the thermodynamics of the ICM even for one of its faintest clusters after a careful treatment of the contamination by point sources.