Speaker
Description
Observations of galaxy clusters offer several ways to constrain cosmological models. In particular, the combination of X-ray and millimetre observations of their intracluster medium can be used to measure the Hubble constant, $H_0$, independently of both CMB-based estimates and local distance-ladder measurements. However, the application of this method is limited by several astrophysical and observational systematics. These include deviations from spherical symmetry, gas clumpiness, uncertainties in the chemical composition of the intracluster medium, and approximations in the modelling of the signals.
In this work, we update and extend the $H_0$ inference framework based on the comparison between the spectroscopic X-ray and SZ-based temperature profiles, with the aim of improving the calibration of systematics associated with the modelling of cluster structure and dynamical state. To this end, we use hydrodynamical simulations from The Three Hundred project to characterise the expected mismatch between X-ray and SZ-based thermodynamic reconstructions within a Bayesian framework. We then apply the method to joint Planck SZ and XMM-Newton X-ray observations of 116 galaxy clusters from the CHEX-MATE sample, obtaining updated constraints on $H_0$ from this probe. Finally, we investigate additional observational systematics that may affect the measurement, including the impact of relativistic SZ corrections and assumptions on the chemical composition of the intracluster medium.