Turbulent Heating in Galaxy Clusters Brightest in X-rays

TL;DR

This paper demonstrates that turbulence-driven heating in galaxy cluster cores can effectively counteract radiative cooling, potentially solving the longstanding gas cooling problem in these environments.

Contribution

It introduces a new data-analysis method to directly evaluate ICM heating from turbulence dissipation using Chandra data, showing turbulence as a key heating mechanism.

Findings

Turbulent heating balances radiative cooling locally in cluster cores.

The new method enables direct measurement of ICM heating rates.

Turbulence may be the primary process preventing gas cooling in galaxy clusters.

Abstract

The hot, X-ray-emitting intracluster medium (ICM) is the dominant baryonic constituent of clusters of galaxies. In the cores of many clusters, radiative energy losses from the ICM occur on timescales significantly shorter than the age of the system. Unchecked, this cooling would lead to massive accumulations of cold gas and vigorous star formation, in contradiction to observations. Various sources of energy capable of compensating these cooling losses have been proposed, the most promising being heating by the supermassive black holes in the central galaxies through inflation of bubbles of relativistic plasma. Regardless of the original source of energy, the question of how this energy is transferred to the ICM has remained open. Here we present a plausible solution to this question based on deep Chandra X-ray observatory data and a new data-analysis method that enables us to evaluate directly the ICM heating rate due to the dissipation of turbulence. We find that turbulent heating is sufficient to offset radiative cooling and indeed appears to balance it locally at each radius - it might therefore be the key element in resolving the gas cooling problem in cluster cores and, more universally, in atmospheres of X-ray gas-rich systems.