Creation of X-ray cavities in galaxy clusters with cosmic rays

Abstract

We describe how AGN-produced cosmic rays form large X-ray cavities and radio lobes in the hot diffuse gas in galaxy groups and clusters. Cosmic rays are assumed to be produced in a small shocked region near the cavity center, such as at the working surface of a radio jet. The coupled equations for gasdynamics and cosmic ray diffusion are solved with various assumptions about the diffusion coefficient. To form large, long-lived cavities similar to those observed, the diffusion coefficient must not exceed kappa = 10^28 cm^2/s in the hot gas, very similar to values required in models of cosmic ray diffusion in the Milky Way. When kappa does not exceed 10^28, cosmic rays are confined within the cavities for times comparable to the cavity buoyancy time, as implied by observations of X-ray cavities and their radio synchrotron emission. Collisions of proton cosmic rays with thermal plasma nuclei followed by pion decay can result in enhanced gamma ray emission from the cavity walls.

16 pages, 10 figures, accepted by ApJ

References in corpus (6)

• Magnetic Field in Clusters of Galaxies
• An X-ray study of magnetic field strengths and particle content in FRII radio sources
• Particle Energies and Filling Fractions of Radio Bubbles in Cluster Cores
• MHD Simulations of Relic Radio Bubbles in Clusters
• Simulating field-aligned diffusion of a cosmic ray gas
• The quest for cosmic ray protons in galaxy clusters

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• Thermal and non-thermal traces of AGN feedback: results from cosmological AMR simulations
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• Simulations of cosmic rays in large-scale structures: numerical and physical effects
• Creation of the X-ray Cavity Jet and its Radio Lobe in M87/Virgo with Cosmic Rays; Relevance to Relic Radio Sources
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