Ram pressure stripping in elliptical galaxies: I. the impact of the
  interstellar medium turbulence
  Elliptical galaxies contain X-ray emitting gas that is subject to continuous
ram pressure stripping over timescales comparable to cluster ages. The gas in
these galaxies is not in perfect hydrostatic equilibrium. Supernova feedback,
stellar winds, or active galactic nuclei (AGN) feedback can significantly
perturb the interstellar medium (ISM). Using hydrodynamical simulations, we
investigate the effect of subsonic turbulence in the hot ISM on the ram
pressure stripping process in early-type galaxies. We find that galaxies with
more turbulent ISM produce longer, wider, and more smoothly distributed tails
of the stripped ISM than those characterised by weaker ISM turbulence. Our main
conclusion is that even very weak internal turbulence, at the level of <15% of
the average ISM sound speed, can significantly accelerate the gas removal from
galaxies via ram pressure stripping. The magnitude of this effect increases
sharply with the strength of turbulence. As most of the gas stripping takes
place near the boundary between the ISM and the intraclustermedium (ICM), the
boost in the ISM stripping rate is due to the "random walk" of the ISM from the
central regions of the galactic potential well to larger distances, where the
ram pressure is able to permanently remove the gas from galaxies. The ICM can
be temporarily trapped inside the galactic potential well due to the mixing of
the turbulent ISM with the ICM. The galaxies with more turbulent ISM, yet still
characterised by very weak turbulence, can hold larger amounts of the ICM.
[Abridged]
