Evolution of X-ray Cavities in Galaxy Clusters
  The physics of X-ray cavities in galaxy clusters is constrained by their
observed morphological evolution, which depends on such poorly-understood
properties as the turbulent density field and magnetic fields. Here we combine
numerical simulations that include subgrid turbulence and software that
produces synthetic X-ray observations to examine the evolution of X-ray
cavities in the the absence of magnetic fields. Our results reveal an
anisotropic size evolution that is very different from simplified, analytical
predictions. These differences highlight some of the key issues that must be
accurately quantified when studying AGN-driven cavities, and help to explain
why the inferred pV energy in these regions appears to be correlated with their
distance from the cluster center. Interpreting X-ray observations will require
detailed modeling of effects including mass-entrainment, distortion by drag
forces, and projection. Current limitations do not allow a discrimination
between purely hydrodynamic and magnetically-dominated models for X-ray
cavities.
