Deriving the Hubble constant using Planck and XMM-Newton observations of galaxy clusters

¹ Dipartimento di Fisica, Università di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
e-mail: arpine.kozmanyan@roma2.infn.it
² Sezione INFN Roma 2, Via della Ricerca Scientifica 1, 00133 Roma, Italy
³ INAF, Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy
⁴ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Piero Gobetti 93/3, 40129 Bologna, Italy
⁵ Dipartimento di Fisica e Astronomia, Alma Mater – Universita di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy

Received: 16 July 2018
Accepted: 25 September 2018

Abstract

The possibility of determining the value of the Hubble constant using observations of galaxy clusters in X-ray and microwave wavelengths through the Sunyaev Zel’dovich (SZ) effect has long been known. Previous measurements have been plagued by relatively large errors in the observational data and severe biases induced, for example, by cluster triaxiality and clumpiness. The advent of Planck allows us to map the Compton parameter y, that is, the amplitude of the SZ effect, with unprecedented accuracy at intermediate cluster-centric radii, which in turn allows performing a detailed spatially resolved comparison with X-ray measurements. Given such higher quality observational data, we developed a Bayesian approach that combines informed priors on the physics of the intracluster medium obtained from hydrodynamical simulations of massive clusters with measurement uncertainties. We applied our method to a sample of 61 galaxy clusters with redshifts up to z <  0.5 observed with Planck and XMM-Newton and find H₀ = 67 ± 3 km s⁻¹ Mpc⁻¹.