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

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 łesssim 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 łeff, 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.