Gas thermodynamics meets galaxy kinematics: Joint mass measurements for eROSITA galaxy clusters

The mass of galaxy clusters is a critical quantity for probing cluster cosmology and testing theories of gravity, but its measurement could be biased given assumptions are inevitable.

In this paper, we employ and compare two mass proxies for galaxy clusters: thermodynamics of the intracluster medium and kinematics of member galaxies.

We select 22 galaxy clusters from the cluster catalog in the first SRG/eROSITA All-Sky Survey (eRASS1) that have sufficient optical and near-infrared observations.

We generate multi-band images in the energy range of (0.3, 7) keV for each cluster, and derive their temperature profiles, gas mass profiles and hydrostatic mass profiles using a parametric approach that does not assume dark matter halo models.

With spectroscopically confirmed member galaxies collected from multiple surveys, we numerically solve the spherical Jeans equation for their dynamical mass profiles.

Our results quantify the correlation between dynamical mass and line-of-sight velocity dispersion with an rms scatter of 0.14 dex.

We find the two mass proxies lead to roughly the same total mass, with no observed systematic bias.

As such, the $\sigma_8$ tension is not specific to hydrostatic mass or weak lensing shears, but also appears with galaxy kinematics.

We also compare our hydrostatic masses with the latest weak lensing masses inferred with scaling relations.

The comparison shows the weak lensing mass is significantly higher than our hydrostatic mass by $\sim$110%.

This might explain the significantly larger value of $\sigma_8$ from the latest measurement using eRASS1 clusters than almost all previous estimates in the literature.

Finally, we test the radial acceleration relation (RAR) established in disk galaxies.

We confirm the missing baryon problem in the inner region of galaxy clusters using three independent mass proxies for the first time.

;Comment: 14 pages, 9 figures, 2 tables, with 12-page appendix for additional figures and tables.

Accepted for publication in A&A