CHEX-MATE: Dynamical masses for a sample of 101 Planck Sunyaev-Zeldovich-selected galaxy clusters

Abstract

The Cluster HEritage project with XMM-Newton – Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE) is a programme to study a minimally biased sample of 118 galaxy clusters detected by Planck through the Sunyaev–Zeldovich effect. Accurate and precise mass measurements are required to exploit CHEX-MATE as an astrophysical laboratory and a calibration sample for cosmological probes in the era of large surveys. We measured masses based on the galaxy dynamics, which are highly complementary to weak-lensing or X-ray estimates. We analysed the sample with a uniform pipeline that is stable both for poorly sampled or rich clusters ---using spectroscopic redshifts from public (NED, SDSS, and DESI) or private archives--- and dedicated observational programmes. We modelled the halo mass density and the anisotropy profile. Membership is confirmed with a cleaning procedure in phase space. We derived masses from measured velocity dispersions under the assumed model. We measured dynamical masses for 101 CHEX-MATE clusters with at least ten confirmed members within the virial radius $r_ 200c $. Estimated redshifts and velocity dispersions agree with literature values when available. Validation with weak-lensing masses shows agreement within $8 (stat.) (sys.) \,<!PCT!>$, and confirms dynamical masses as an unbiased proxy. Comparison with Planck masses shows them to be biased low by $34 (stat.) (sys.) \,<!PCT!>$. A follow-up spectroscopic campaign is underway to cover the full CHEX-MATE sample.