Stirred, not Clumped: Evolution of Temperature Profiles in the Outskirts of Galaxy Clusters

TL;DR

This paper investigates how non-thermal gas motions caused by mergers and accretion influence the temperature profiles in galaxy cluster outskirts, challenging previous assumptions about substructure effects.

Contribution

It demonstrates that non-thermal motions explain deviations from self-similar evolution in cluster outskirts, emphasizing their role over gaseous substructures.

Findings

Non-thermal gas motions drive temperature profile deviations.

Gaseous substructures have minor impact on temperature evolution.

Proper halo overdensity definitions reduce observed deviations.

Abstract

Recent statistical X-ray measurements of the intracluster medium (ICM) indicate that gas temperature profiles in the outskirts of galaxy clusters deviate from self-similar evolution. Using a mass-limited sample of galaxy clusters from cosmological hydrodynamical simulations, we show that the departure from self-similarity can be explained by non-thermal gas motions driven by mergers and accretion. Contrary to previous claims, gaseous substructures only play a minor role in the temperature evolution in cluster outskirts. A careful choice of halo overdensity definition in self-similar scaling mitigates these departures. Our work highlights the importance of non-thermal gas motions in ICM evolution and the use of galaxy clusters as cosmological probes.