2022MNRAS.514.3765C

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 (>=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 maximize 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 \lesssim 20 per cent (in some directions) of the injected power can be carried away by sound flux in the intermediate feedback but it reduces to \lesssim 10 per cent (in some directions) 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.