Kinematics of filaments in cooling flow clusters and heating by mixing

TL;DR

This paper investigates the kinematics of optical filaments in galaxy clusters, showing that jet-induced vortexes better explain their velocity structures than turbulence, and suggests mixing with hot bubbles as a more efficient heating mechanism.

Contribution

It demonstrates that filament velocities are better explained by jet-induced vortexes rather than turbulent cascade, highlighting the role of mixing in heating the intracluster medium.

Findings

Filament velocity structures are steeper than classical turbulence predictions.

Jet-inflated bubbles generate vortexes across multiple scales.

Mixing heating is more efficient than turbulent dissipation.

Abstract

We compare a recent study of the kinematics of optical filaments in three cooling flow clusters of galaxies with previous numerical simulations of jet-inflated hot bubbles, and conclude that the velocity structure functions of the filaments better fit direct excitation by the jets than by turbulent cascade from the largest turbulent eddies. The observed velocity structure functions of the optical filaments in the three clusters are steeper than that expected from a classical cascade in turbulent dissipation. Our three-dimensional (3D) hydrodynamical simulations show that as the jets inflate bubbles in the intracluster medium (ICM), they form vortexes in a large range of scales. These vortexes might drive the ICM turbulence with eddies of over more than an order of magnitude in size. A direct excitation of turbulence by the vortexes that the jets form and the slow turbulent dissipation imply that heating the ICM by mixing with hot bubbles is more efficient than heating by turbulent dissipation.