Galaxy cluster temperature maps from joint X-ray and tSZ maps with The Three Hundred hydrodynamical simulations

¹ Dipartimento di Fisica, Sapienza Università di Roma, Piazzale Aldo Moro 5, I-00185 Roma, Italy
² INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monteporzio Catone, Italy
³ Physics Department “Ettore Pancini”, Università degli studi di Napoli “Federico II”, Via Cintia 21, I-80126 Napoli, Italy
⁴ INAF/IASF-Milano, Via A. Corti 12, 20133 Milano, Italy
⁵ Departamento de Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain
⁶ Centro de Investigación Avanzada en Física Fundamental (CIAFF), Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
⁷ INAF-Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
⁸ IFPU-Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
⁹ Department of Physics, University of Michigan, 450 Church St, Ann Arbor, MI 48109, USA
¹⁰ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
¹¹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
¹² Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 53, avenue des Martyrs, 38000 Grenoble, France
¹³ Institut de Radioastronomie Millimétrique (IRAM), Avenida Divina Pastora 7, Local 20, E-18012 Granada, Spain

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Received: 7 November 2025
Accepted: 25 March 2026

Abstract

Galaxy clusters can be used as powerful cosmological probes, provided one can obtain accurate mass estimates, which requires a precise knowledge of the underlying astrophysics of galaxy clusters. For these purposes, spatially resolved measurements of the thermodynamic properties of the intracluster medium (ICM), such as density and temperature, are necessary. In particular, temperature estimates are traditionally obtained through spatially resolved X-ray spectroscopy. Such measurements suffer from their sensitivity to the chosen energy calibration, may exhibit inherent biases, and are especially hard to perform at high redshift as they require deep observations. In recent years, however, millimeter wavelength data with high spatial resolution, comparable to that of current X-ray telescopes, have begun to be available. This has enabled the development of new methods to infer and map the cluster temperature in individual clusters, using the combination of density maps from X-ray data and pressure maps from millimeter data. In this paper, we present the first systematic validation of this approach on a large sample of synthetic clusters generated in The Three Hundred hydrodynamical simulations. We show that we are able to recover theoretical estimates of the temperature, namely the mass-weighted and spectroscopic-like temperatures, within biases of the order of ≲1% in the best cases, up to ∼10% in average, with scatters on the order of 10%. To prepare the application of this approach to observed data, we discuss the modeling of the effective length l_eff, a key quantity necessary for the combination of X-ray and thermal Sunyaev-Zel’dovich projected data. In particular we provide templates calibrated on simulations for this quantity, and investigate their impact on the recovery of the temperature map, compared to other standard models.