CHEX-MATE: Characterization of the intra-cluster medium temperature distribution

¹ INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, 40129 Bologna, Italy
e-mail: lorenzo.lovisari@inaf.it
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
³ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴ INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste, Italy
⁵ Institute of Fundamental Physics of the Universe, Via Beirut 2, 34151 Grignano, Trieste, Italy
⁶ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
⁷ Dipartimento di Fisica, Universitá di Roma ‘Tor Vergata’, Via della Ricerca Scientifica 1, 00133 Roma, Italy
⁸ INFN, Sezione di Roma ‘Tor Vergata’, Via della Ricerca Scientifica, 1, 00133 Roma, Italy
⁹ Dipartimento di Fisica e Astronomia, Universitá di Bologna, Via Gobetti 92/3, 40121 Bologna, Italy
¹⁰ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
¹¹ INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
¹² Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale Aldo Moro, 00185 Roma, Italy
¹³ Department of Astronomy, University of Geneva, Ch. d’Ecogia 16, 1290 Versoix, Switzerland
¹⁴ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
¹⁵ California Institute of Technology, 1200 E. California Blvd, MC367-17, Pasadena, CA 91125, USA
¹⁶ H. H. Wills Physics Laboratory, University of Bristol, Tyndall Ave, Bristol BS8 1TL, UK
¹⁷ IRAP, Université de Toulouse, CNRS, CNES, UT3-UPS, 31400 Toulouse, France
¹⁸ Université Paris-Saclay, Université Paris-Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹⁹ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
²⁰ INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50122 Firenze, Italy

Received: 14 April 2023
Accepted: 29 October 2023

Abstract

Context. Galaxy clusters grow through the accretion of mass over cosmic time. Their observed properties are then shaped by how baryons distribute and energy is diffused. Thus, a better understanding of spatially resolved, projected thermodynamic properties of the intra-cluster medium (ICM) may provide a more consistent picture of how mass and energy act locally in shaping the X-ray observed quantities of these massive virialized or still collapsing structures.

Aims. We study the perturbations in the temperature (and density) distribution to evaluate and characterize the level of inhomogeneities and the related dynamical state of the ICM.

Methods. We obtain and analyze the temperature and density distribution for 28 clusters (2.4 × 10¹⁴ M_⊙ < M₅₀₀ < 1.2 × 10¹⁵ M_⊙; 0.07 < z < 0.45) selected from the CHEX-MATE sample. We use these spatially resolved two-dimensional distributions to measure the global and radial scatter and identify the regions that deviate the most from the average distribution. During this process, we introduce three dynamical state estimators and produce “clean” temperature profiles after removing the most deviant regions.

Results. We find that the temperature distribution of most of the clusters is skewed towards high temperatures and is well described by a log-normal function. There is no indication that the number of regions deviating more than 1σ from the azimuthal value is correlated with the dynamical state inferred from morphological estimators. The removal of these regions leads to local temperature variations up to 10–20% and an average increase of ∼5% in the overall cluster temperatures. The measured relative intrinsic scatter within R₅₀₀, σ_T, int/T, has values of 0.17_−0.05^+0.08, and is almost independent of the cluster mass and dynamical state. Comparing the scatter of temperature and density profiles to hydrodynamic simulations, we constrain the average Mach number regime of the sample to Ṁ_3D = 0.36_−0.09^+0.16. We infer the ratio between the energy in turbulence and the thermal energy, and translate this ratio in terms of a predicted hydrostatic mass bias b, estimating an average value of b ∼ 0.11 (covering a range between 0 and 0.37) within R₅₀₀.

Conclusions. This study provides detailed temperature fluctuation measurements for 28 CHEX-MATE clusters which can be used to study turbulence, derive the mass bias, and make predictions on the scaling relation properties.