CHEX-MATE: Morphological analysis of the sample

¹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, via Piero Gobetti 93/3, 40129 Bologna, Italy
e-mail: maria.campitiello@inaf.it
² Dipartimento di Fisica e Astronomia, Universitá di Bologna, via Gobetti 92/3, 40121 Bologna, Italy
³ INFN, Sezione di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴ Center for Astrophysics – Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁵ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, via A. Corti 12, 20133 Milano, Italy
⁶ Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
⁷ Dipartimento di Fisica, Sezione di Astronomia, Universitá di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁸ Institute of Fundamental Physics of the Universe, via Beirut 2, 34151 Grignano, Trieste, Italy
⁹ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
¹⁰ H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
¹¹ IRAP, Université de Toulouse, CNRS, CNES, UPS, 9 Avenue du colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
¹² IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, 34014 Trieste, Italy
¹³ University Observatory Munich, Scheinerstr. 1, 81679 Munich, Germany
¹⁴ INAF – Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
¹⁵ INFN – Sezione di Trieste, Trieste, Italy
¹⁶ Universitá degli studi di Roma ‘Tor Vergata’, via della ricerca scientifica, 1, 00133 Roma, Italy
¹⁷ Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale Aldo Moro 5, 00185 Roma, Italy
¹⁸ Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544-1001, USA

Received: 3 March 2022
Accepted: 20 May 2022

Abstract

A classification of the galaxy cluster’s dynamical state is crucial when dealing with large samples. The identification of the most relaxed and most disturbed objects is necessary for both cosmological analysis, focused on spherical and virialised systems, and astrophysical studies, centred around all those micro-physical processes that take place in disturbed clusters (such as particle acceleration or turbulence). Among the most powerful tools for the identification of the dynamical state of clusters is the analysis of their intracluster medium (ICM) distribution. In this work, we performed an analysis of the X-ray morphology of the 118 (Cluster HEritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation) CHEX-MATE clusters, with the aim of providing a classification of their dynamical state. To investigate the link between the X-ray appearance and the dynamical state, we considered four morphological parameters: the surface brightness concentration, the centroid shift, and the second- and third-order power ratios. These indicators result to be strongly correlated with each other, powerful in identifying the disturbed and relaxed population, characterised by a unimodal distribution, and not strongly influenced by systematic uncertainties. In order to obtain a continuous classification of the CHEX-MATE objects, we combined these four parameters in a single quantity, M, which represents the grade of relaxation of a system. On the basis of the M value, we identified the most extreme systems of the sample, finding 15 very relaxed and 27 very disturbed galaxy clusters. From a comparison with previous analysis on X-ray selected samples, we confirmed that the Sunyaev-Zeldovich (SZ) clusters tend to be more disturbed. Finally, by applying our analysis to a simulated sample, we found a general agreement between the observed and simulated results, with the only exception being the concentration. This latter behaviour is partially related to the presence of particles with a high smoothed-particle-hydrodynamics density in the central regions of the simulated clusters due to the action of the idealised isotropic thermal active galactic nucleus (AGN) feedback.