Limits on turbulent propagation of energy in cool-core clusters of galaxies

TL;DR

This study constrains the velocity of turbulence in galaxy cluster cores, showing it is insufficient for energy propagation needed to offset cooling, thus challenging some models of turbulent heating in AGN feedback.

Contribution

It extends previous turbulence constraints from Perseus to additional clusters, providing new limits on turbulent velocities relevant for heating models.

Findings

Turbulent velocities are too low to propagate energy to the cooling radius within the cooling time.

Results challenge models requiring turbulence to rapidly resupply energy for cooling offset.

Constraints are based on Reflection Grating Spectrometer measurements of line broadening.

Abstract

We place constraints on the propagation velocity of bulk turbulence within the intracluster medium of three clusters and an elliptical galaxy. Using Reflection Grating Spectrometer measurements of turbulent line broadening, we show that for these clusters, the 90% upper limit on turbulent velocities when accounting for instrumental broadening is too low to propagate energy radially to the cooling radius of the clusters within the required cooling time. In this way, we extend previous Hitomi-based analysis on the Perseus cluster to more clusters, with the intention of applying these results to a future, more extensive catalog. These results constrain models of turbulent heating in AGN feedback by requiring a mechanism which can not only provide sufficient energy to offset radiative cooling, but resupply that energy rapidly enough to balance cooling at each cluster radius.