Evolution of X-ray cavities
  A wide range of recent observations have shown that AGN-driven cavities may
provide the energy source that balances the cooling observed in the centres of
cool-core galaxy clusters. One tool for better understanding the physics of
these cavities is their observed morphological evolution, which is dependent on
such poorly-understood properties as the turbulent density field and the impact
of 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 absence of magnetic fields. Our results
reveal an anisotropic size evolution of that is dramatically 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 pro jection. Current
limitations do not allow a discrimination between purely hydrodynamic and
magnetically-dominated models for X-ray cavities.
