Acoustic waves and g-mode turbulence as energy carriers in a viscous
  intracluster medium
  Many recent works on the observed galaxy clusters in the X-rays highlight
broadly two classes of exclusive energy carriers - sound waves and turbulence.
In order to understand this dichotomy, we design an idealized three-dimensional
hydrodynamic simulation of a cluster, to assess which of these carriers can
dissipate energy in and around the core ($\gtrsim 100$ kpc) . Specifically, we
explore how gentle (long-duration outbursts) and intermediate (shorter duration
outbursts) feedback modes can function efficiently mediated by compressible
(sound waves) and incompressible (g-modes/instabilities/turbulence)
disturbances. Since g-modes are confined tightly to the central core, we
attempt to maximise the flux of fast sound waves to distribute the feedback
energy over a large distance. We find that the contribution to heat dissipation
from sound and turbulence varies on the basis of the aforementioned feedback
modes, namely: turbulence contributes relatively more than sound in the
slow-piston regime and vice versa for the intermediate regime. For the first
time in a 3D simulation, we show that up to $\sim 20\%$ of the injected power
can be carried away by sound flux in the intermediate feedback but it reduces
to $\sim 12 \%$ in the slow-piston regime. Lastly, we find that sound waves can
be elusive if we deduce the equation-of-state (isobaric/isentropic) of the
fluctuations from X-ray observations.
