CHEX-MATE: Relationship between X-ray and millimetre inferences of galaxy cluster temperature profiles

¹ Dipartimento di Fisica, Università di Roma ‘Tor Vergata’ Via della Ricerca Scientifica 1 I-00133 Roma, Italy
² INFN, Sezione di Roma ‘Tor Vergata’, Via della Ricerca Scientifica 1 00133 Roma, Italy
³ Space Science Data Center, Italian Space Agency Via del Politecnico 00133 Roma, Italy
⁴ High Energy Physics Division, Argonne National Laboratory Lemont IL 60439, USA
⁵ Dipartimento di Fisica, Sapienza Università di Roma Piazzale Aldo Moro 5 I-00185 Rome, Italy
⁶ Department of Astronomy, University of Geneva Ch. d’Ecogia 16 CH-1290 Versoix, Switzerland
⁷ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna Via Piero Gobetti 93/3 I-40129 Bologna, Italy
⁸ INFN, Sezione di Bologna Viale Berti Pichat 6/2 I-40127 Bologna, Italy
⁹ Dipartimento di Fisica ‘E. Pancini’, Università degli Studi di Napoli Federico II, Via Cinthia 21 I-80126 Napoli, Italy
¹⁰ Center for Astrophysics | Harvard & Smithsonian 60 Garden Street Cambridge MA 02138, USA
¹¹ Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia 41125 Modena, Italy
¹² INAF – IASF Milano Via A. Corti 12 I-20133 Milano, Italy
¹³ Dipartimento di Fisica e Astronomia (DIFA), Alma Mater Studiorum – Università di Bologna Via Gobetti 93/2 40129 Bologna, Italy
¹⁴ Istituto Nazionale di Astrofisica – Istituto di Radioastronomia (IRA) Via Gobetti 101 40129 Bologna, Italy
¹⁵ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester Manchester M13 9PL, UK
¹⁶ Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro Yuseong-gu Daejeon 34141, Republic of Korea
¹⁷ Université Grenoble Alpes, CNRS, LPSC-IN2P3, 53 avenue des Martyrs 38000 Grenoble, France
¹⁸ HH Wills Physics Laboratory, University of Bristol Bristol BS8 1TL, UK
¹⁹ IRAP, CNRS, Université de Toulouse, CNES, UT3-UPS Toulouse, France
²⁰ INFN, Sezione di Genova Via Dodecaneso 33 16146 Genova, Italy
²¹ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM 91191 Gif-sur-Yvette, France
²² INAF – Osservatorio Astronomico di Trieste Via Tiepolo 11 I-34131 Trieste, Italy
²³ IFPU, Institute for Fundamental Physics of the Universe Via Beirut 2 34014 Trieste, Italy
²⁴ Department of Physics, University of Michigan Ann Arbor MI 48109, USA
²⁵ California Institute of Technology 1200 East California Boulevard Pasadena California, USA

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Received: 21 October 2025
Accepted: 23 December 2025

Abstract

Thermodynamic profiles from X-ray and millimetre observations of galaxy clusters are often compared under the simplifying assumptions of a smooth, spherically symmetric intracluster medium. These approximations lead to expected discrepancies in the inferred profiles, which can provide insights into the cluster structure or cosmology. Motivated by this, we present a joint XMM-Newton and Planck analysis of 116 CHEX-MATE clusters to measure η_T = T_X/T_SZ, X, the ratio between spectroscopic X-ray temperatures and a temperature proxy derived from Sunyaev-Zel’dovich (SZ) pressures and X-ray densities. We considered relativistic corrections to the thermal SZ signal and implemented X-ray absorption by Galactic molecular hydrogen. The η_T distribution has a mean of 1.01 ± 0.03, with average changes of 8.1% and 2.7% when relativistic corrections and molecular hydrogen absorption are not included, respectively. The η_T distribution is positively skewed, with the scatter mostly affected by cluster morphology: relaxed clusters are closer to unity and less scattered than mixed and disturbed systems. We find little or no correlation with redshift, mass, or temperature.