Constraining gas motion and non-thermal pressure beyond the core of the Abell 2029 galaxy cluster with XRISM

TL;DR

This study uses XRISM high-resolution spectroscopy to measure gas motions and non-thermal pressure in the galaxy cluster Abell 2029, finding minimal non-thermal pressure contribution and small hydrostatic mass bias beyond the core.

Contribution

First detailed measurement of gas velocities and non-thermal pressure in Abell 2029 beyond the core using XRISM data, challenging simulation predictions.

Findings

Non-thermal pressure accounts for no more than 2% of total pressure at all radii.

Hydrostatic mass bias is approximately 2% across the observed region.

Radial trend of non-thermal pressure differs from many numerical simulations.

Abstract

We report a detailed spectroscopic study of the gas dynamics and hydrostatic mass bias of the galaxy cluster Abell 2029, utilizing high-resolution observations from XRISM Resolve. Abell 2029, known for its cool core and relaxed X-ray morphology, provides an excellent opportunity to investigate the influence of gas motions beyond the central region. Expanding upon prior studies that revealed low turbulence and bulk motions within the core, our analysis covers regions out to the scale radius $R_{2500}$ (670~kpc) based on three radial pointings extending from the cluster center toward the northern side. We obtain accurate measurements of bulk and turbulent velocities along the line of sight. The results indicate that non-thermal pressure accounts for no more than 2% of the total pressure at all radii, with a gradual decrease outward. The observed radial trend differs from many numerical simulations, which often predict an increase in non-thermal pressure fraction at larger radii. These findings suggest that deviations from hydrostatic equilibrium are small, leading to a hydrostatic mass bias of around 2% across the observed area.