The Role of Penetrating Gas Streams in Setting the Dynamical State of Galaxy Clusters

TL;DR

This study uses cosmological simulations to show that penetrating gas streams from the cosmic web influence the dynamical state and X-ray properties of galaxy clusters, affecting their relaxation and internal motions.

Contribution

It reveals how inflowing streams from the cosmic web impact cluster dynamics and morphology, highlighting the role of heated gas streams in cluster relaxation processes.

Findings

Unrelaxed clusters have higher inflow rates and deeper stream penetration.

Penetrating streams induce bulk motions, cold fronts, and increased turbulence.

Clusters can transition from unrelaxed to relaxed states over several gigayears.

Abstract

We utilize cosmological simulations of 16 galaxy clusters at redshifts \zeq{0} and \zeq{0.6} to study the effect of inflowing streams on the properties of the X-ray emitting intracluster medium. We find that the mass accretion occurs predominantly along streams that originate from the cosmic web and consist of heated gas. Clusters that are unrelaxed in terms of their X-ray morphology are characterized by higher mass inflow rates and deeper penetration of the streams, typically into the inner third of the virial radius. The penetrating streams generate elevated random motions, bulk flows and cold fronts. The degree of penetration of the streams may change over time such that clusters can switch from being unrelaxed to relaxed over a time-scale of several giga years.