Do sound waves transport the AGN energy in the Perseus Cluster?

TL;DR

This paper investigates whether sound waves can effectively transport energy in the Perseus Cluster's core, finding that sound waves travel fast enough to distribute energy and match observed gas variations, unlike turbulence or gravity waves.

Contribution

It demonstrates that sound waves are a viable mechanism for energy transport in the cluster core, aligning with observational data and overcoming limitations of turbulence and gravity waves.

Findings

Sound waves travel at about 1000 km/s in the cluster core.

Sound waves can cross the core within the cooling time.

Gas displacement velocities are consistent with observations.

Abstract

The level of random motions in the intracluster gas lying between 20 and 60 kpc radius in the core of the Perseus cluster has been measured by the Hitomi Soft X-ray Spectrometer at 164 +/- 10 km/s. The maximum energy density in turbulent motions on that scale is therefore low. If dissipated as heat the turbulent energy will be radiated away in less than 80 Myr and cannot spread across the core. A higher velocity is needed to prevent a cooling collapse. Gravity waves are shown to travel too slowly in a radial direction. Here we investigate propagation of energy by sound waves. The energy travels at about 1000 km/s and can cross the core in a cooling time. We show that the displacement velocity amplitude of the gas required to carry the power is consistent with the Hitomi result and that the inferred density and temperature variations are consistent with Chandra observations.