All Curled up: A Numerical Investigation of Shock-Bubble Interactions and the Role of Vortices in Heating Galaxy Clusters

Type Journal Article
Names Samuel H. Friedman, Sebastian Heinz, Eugene Churazov
Publication The Astrophysical Journal
Volume 746
Issue 1
Pages 112
Date February 1, 2012
Short Title All Curled up
Library Catalog NASA ADS
Abstract Jets from active galactic nuclei (AGNs) in the centers of galaxy clusters inflate cavities of low-density relativistic plasma and drive shock and sound waves into the intracluster medium. When these waves overrun previously inflated cavities, they form a differentially rotating vortex through the Richtmyer-Meshkov instability (RMI). The dissipation of energy captured in the vortex can contribute to the feedback of energy into the atmospheres of cool core clusters. Using a series of hydrodynamic simulations, we investigate the efficiency of this process: we calculate the kinetic energy in the vortex by decomposing the velocity field into its irrotational and solenoidal parts. Compared to the two-dimensional case, the three-dimensional RMI is about a factor of two more efficient. The energy in the vortex field for weak shocks is E vortex ≈ ρICMΔ v 2 shock V bubble (with dependence on the geometry, density contrast, and shock width). For strong shocks, the vortex becomes dynamically unstable, quickly dissipating its energy via a turbulent cascade. We derive a number of diagnostics for observations and laboratory experiments of shock-bubble interactions, like the shock-vortex standoff distance, which can be used to derive lower limits on the Mach number. The differential rotation of the vortex field leads to viscous dissipation, which is sufficiently efficient to react to cluster cooling and to dissipate the vortex energy within the cooling radius of the cluster for a reasonable range of vortex parameters. For sufficiently large filling factors (of order a few percent or larger), this process could thus contribute significantly to AGN feedback in galaxy clusters.
Tags GALAXIES: CLUSTERS: GENERAL, ISM: bubbles, Instabilities, Methods: Numerical, hydrodynamics, shock waves
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