# Line-of-sight gas sloshing in the cool core of Abell 907

## TL;DR

This study reports the first detection of line-of-sight gas sloshing in the cool core of galaxy cluster Abell 907, revealing complex gas dynamics and their impact on cluster heating.

## Contribution

It provides the first evidence of line-of-sight gas sloshing in a galaxy cluster's cool core, expanding understanding of gas motions beyond plane-of-sky observations.

## Key findings

- Detected a redshift difference indicating velocity shear of ~1680 km/s.
- Gas sloshing contributes to non-thermal pressure support (~34%).
- Kinetic energy from sloshing is about 30% of the cluster's bolometric luminosity.

## Abstract

We present line-of-sight gas sloshing first found in a cool core in a galaxy cluster. The galaxy cluster Abell 907 is identified as a relaxed cluster owing to its global X-ray surface brightness taken by the Chandra X-ray Observatory. The X-ray residual image after removing the global emission of the intracluster medium (ICM), however, shows an arc-like positive excess and a negative excess surrounding the central positive excess in the cluster core, which in turn indicates a disturbance of the ICM. We analyze the X-ray spectra extracted from both regions and find that (1) the ICM temperature and the metal abundance in the positive excess are lower and higher than those in the negative excess, respectively, and (2) the ICM is nearly in pressure equilibrium. We also find a slight redshift difference between the positive and the negative excesses, which corresponds to the velocity shear of $1680^{+1300}_{-920}$ km s$^{-1}$ ($1\sigma$). The X-ray residual image and the ICM properties are consistent with those expected by line-of-sight gas sloshing. Assuming that the gas is moving toward inverse-parallel to each other along the line-of-sight, the shear velocity is expected to be $\sim 800$ km s$^{-1}$. The velocity field of this level is able to provide non-thermal pressure support by $\sim 34\%$ relative to the thermal one. The total kinetic energy inferred from the shear velocity corresponds to $\sim 30\%$ of the bolometric luminosity of the sloshing ICM. Abell 907 is therefore complementary to galaxy clusters in which gas sloshing takes place in the plane of the sky, and is important for understanding gas dynamics driven by sloshing and its influence on the heating to prevent runaway cooling.