CHEX-MATE: Constraining the origin of the scatter in galaxy cluster radial X-ray surface brightness profiles

¹ INAF, IASF-Milano, Via A. Corti 12, 20133 Milano, Italy
e-mail: iacopo.bartalucci@inaf.it
² INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
³ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
⁴ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁵ Department of Astronomy, University of Geneva, ch. d’Écogia 16, 1290 Versoix, Switzerland
⁶ DiSAT, Università degli Studi dell’Insubria, Via Valleggio 11, 22100 Como, Italy
⁷ Astronomy Unit, Department of Physics, University of Trieste, Via Tiepolo 11, 34131 Trieste, Italy
⁸ Università degli studi di Roma ‘Tor Vergata’, Via della ricerca scientifica 1, 00133 Roma, Italy
⁹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, 40129 Bologna, Italy
¹⁰ Dipartimento di Fisica e Astronomia, Universitá di Bologna, Via Gobetti 92/3, 40121 Bologna, Italy
¹¹ INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
¹² Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy
¹³ INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
¹⁴ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
¹⁵ Laboratoire d’Astrophysique de Marseille, Aix-Marseille Université, CNRS, CNES, Marseille, France
¹⁶ Institut d’Astrophysique de Paris, CNRS, Sorbonne Université, 98 bis Bd Arago, 75014 Paris, France
¹⁷ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester M13 9PL, UK
¹⁸ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
¹⁹ HH Wills Physics Laboratory, University of Bristol, Tyndall Ave, Bristol BS8 1TL, UK
²⁰ IRAP, Université de Toulouse, CNRS, CNES, UPS, 9 av. du Colonel Roche, BP44346, 31028 Toulouse Cedex 4, France
²¹ Dipartimento di Fisica, Università degli Studi di Milano, Via G. Celoria 16, 20133 Milano, Italy

Received: 20 February 2023
Accepted: 18 April 2023

Abstract

We investigate the statistical properties and the origin of the scatter within the spatially resolved surface brightness profiles of the CHEX–MATE sample, formed by 118 galaxy clusters selected via the SZ effect. These objects have been drawn from the Planck SZ catalogue and cover a wide range of masses, M₅₀₀ = [2 − 15]×10¹⁴ M_⊙, and redshift, z = [0.05, 0.6]. We derived the surface brightness and emission measure profiles and determined the statistical properties of the full sample and sub-samples according to their morphology, mass, and redshift. We found that there is a critical scale, R ∼ 0.4R₅₀₀, within which morphologically relaxed and disturbed object profiles diverge. The median of each sub-sample differs by a factor of ∼10 at 0.05R₅₀₀. There are no significant differences between mass- and redshift-selected sub-samples once proper scaling is applied. We compare CHEX–MATE with a sample of 115 clusters drawn from the THE THREE HUNDRED suite of cosmological simulations. We found that simulated emission measure profiles are systematically steeper than those of observations. For the first time, the simulations were used to break down the components causing the scatter between the profiles. We investigated the behaviour of the scatter due to object-by-object variation. We found that the high scatter, approximately 110%, at R < 0.4R₅₀₀^Y_SZ is due to a genuine difference between the distribution of the gas in the core of the clusters. The intermediate scale, R₅₀₀^Y_SZ = [0.4−0.8], is characterised by the minimum value of the scatter on the order of 0.56, indicating a region where cluster profiles are the closest to the self-similar regime. Larger scales are characterised by increasing scatter due to the complex spatial distribution of the gas. Also for the first time, we verify that the scatter due to projection effects is smaller than the scatter due to genuine object-by-object variation in all the considered scales.