Creation of X-Ray Cavities in Galaxy Clusters with Cosmic Rays

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 gas dynamics 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 1028 cm2 s1 in the hot gas, very similar to values required in models of cosmic ray diffusion in the Milky Way. When P1028 cm2 s1 , 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 0-decays can result in enhanced gamma-ray emission from the cavity walls.