CHEX-MATE: The intracluster medium entropy distribution in the gravity-dominated regime

¹ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, via A. Corti 12, 20133 Milano, Italy
² Università degli Studi di Milano, via G. Celoria 16, 20133 Milano, Italy
³ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
⁴ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁵ INAF, Osservatorio di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
⁶ IFPU, Institute for Fundamental Physics of the Universe, Via Beirut 2, 34014 Trieste, Italy
⁷ Laboratoire d’Astrophysique de Marseille, CNRS, Aix-Marseille Université, CNES, Marseille, France
⁸ Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université, 98 bis boulevard Arago, 75014 Paris, France
⁹ Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), No. 1, Section 4, Roosevelt Road, Taipei 106216, Taiwan
¹⁰ Dipartimento di Scienza e Alta Tecnologia, Università dell’Insubria, Via Valleggio 11, 22100 Como, Italy
¹¹ Dipartimento di Fisica e Astronomia DIFA – Università di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
¹² INAF – Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
¹³ Dipartimento di Fisica, Università di Roma ‘Tor Vergata’, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁴ INFN, Sezione di Roma ‘Tor Vergata’, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁵ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
¹⁶ Department of Astronomy, University of Geneva, ch. d’Éogia 16, CH-1290 Versoix, Switzerland
¹⁷ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, 40129 Bologna, Italy
¹⁸ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
¹⁹ Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, 41125 Modena, Italy
²⁰ Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
²¹ HH Wills Physics Laboratory, University of Bristol, Tyndall Ave, Bristol BS8 1TL, UK
²² IRAP, CNRS, Université de Toulouse, CNES, UT3-UPS, Toulouse, France
²³ California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA

^⋆ Corresponding author; giacomo.riva@inaf.it

Received: 11 July 2024
Accepted: 8 October 2024

Abstract

We characterise the intracluster gas entropy profiles of 32 very high-mass (M₅₀₀ > 7.75 × 10¹⁴ M_⊙) Planck SZ-detected galaxy clusters (HIGHMz), selected from the CHEX-MATE sample, allowing us to study the intracluster medium (ICM) entropy distribution in a regime where non-gravitational effects are expected to be minimised. Using XMM-Newton measurements, we determined the entropy profiles up to ∼R₅₀₀ for all objects. We assessed the relative role of gas density and temperature measurements on the uncertainty in entropy reconstruction, showing that in the outer regions the largest contribution comes from the temperature. The scaled profiles exhibit a large dispersion in the central regions, but converge rapidly to the value expected from simple gravitational collapse beyond the core regions. We quantified the correlation between the ICM morphological parameters and scaled entropy as a function of radius, showing that centrally peaked objects have low central entropy, while morphologically disturbed objects have high central entropy. We compared the scaled HIGHMz entropy profiles to results from other observational samples, finding differences in normalisation, which appear linked to the average mass of the samples in question. Combining HIGHMz with other samples, we found that a weaker mass dependence than self-similar in the scaling (A_m ∼ −0.25) allows us to minimise the dispersion in the radial range [0.3 − 0.8] R₅₀₀ for clusters spanning over a decade in mass. The deviation from self-similar predictions is radially dependent and is more pronounced at small and intermediate radii than at R₅₀₀. We also investigated the distribution of central entropy K₀, finding no evidence for bimodality in the data and outer slope α, which peaks at α ∼ 1.1 with tails at both low and high α that correlate with dynamical state. Using weak-lensing masses for half of the sample, we found an indication for a small suppression of the scatter (∼30%) beyond the core when using masses derived from Y_X in the rescaling. Finally, we compared our results to recent cosmological numerical simulations from THE THREE HUNDRED and MACSIS, finding good agreement with the observational data in this mass regime. These results provide a robust observational benchmark in the gravity-dominated regime, and will serve as a future reference for samples at lower masses, higher redshifts, and for ongoing work using cosmological numerical simulations.