Simulating the interaction of jets with the intra-cluster medium
  Jets from supermassive black holes in the centres of galaxy clusters are a
potential candidate for moderating gas cooling and subsequent star formation
through depositing energy in the intra-cluster gas. In this work, we simulate
the jet-intra-cluster medium interaction using the moving-mesh
magnetohydrodynamics code Arepo. Our model injects supersonic, low density,
collimated and magnetised outflows in cluster centres, which are then stopped
by the surrounding gas, thermalise and inflate low-density cavities filled with
cosmic-rays. We perform high-resolution, non-radiative simulations of the lobe
creation, expansion and disruption, and find that its dynamical evolution is in
qualitative agreement with simulations of idealised low-density cavities that
are dominated by a large-scale Rayleigh-Taylor instability. The buoyant rising
of the lobe does not create energetically significant small-scale chaotic
motion in a volume-filling fashion, but rather a systematic upward motion in
the wake of the lobe and a corresponding back-flow perpendicular to it. We find
that, overall, 50 per cent of the injected energy ends up in material which is
not part of the lobe, and about 25 per cent remains in the inner 100 kpc. We
conclude that jet-inflated, buoyantly rising cavities drive systematic gas
motions which play an important role in heating the central regions, while
mixing of lobe material is sub-dominant. Encouragingly, the main mechanisms
responsible for this energy deposition can be modelled already at resolutions
within reach in future, high-resolution cosmological simulations of galaxy
clusters.
