The turbulent pressure support in galaxy clusters revisited

TL;DR

This paper investigates the role of turbulence in supporting galaxy clusters against gravity, finding that only about 10% of the total pressure at the virial radius is due to turbulent motions after careful analysis.

Contribution

It provides a detailed analysis of turbulent pressure support in galaxy clusters, disentangling bulk and small-scale motions to refine estimates of non-thermal pressure contributions.

Findings

Turbulent pressure support is approximately 10% at R200.

Radial inflows can bias estimates of non-thermal support.

Careful disentangling reduces overestimation of turbulence effects.

Abstract

Due to their late formation in cosmic history, clusters of galaxies are not fully in hydrostatic equilibrium and the gravitational pull of their mass at a given radius is expected not to be entirely balanced by the thermal gas pressure. Turbulence may supply additional pressure, and recent (X-ray and SZ) hydrostatic mass reconstructions claim a pressure support of $\sim 5-15\%$ of the total pressure at $R_{\rm 200}$. In this work we show that, after carefully disentangling bulk from small-scale turbulent motions in high-resolution simulations of galaxy clusters, we can constrain which fraction of the gas kinetic energy effectively provides pressure support in the cluster's gravitational potential. While the ubiquitous presence of radial inflows in the cluster can lead to significant bias in the estimate of the non-thermal pressure support, we report that only a part of this energy effectively acts as a source of pressure, providing a support of the order of $\sim 10\%$ of the total pressure at $R_{\rm 200}$.