The role of the Rayleigh-Taylor instability in ram pressure stripped disk galaxies

TL;DR

This paper investigates the role of Rayleigh-Taylor instability in ram pressure stripping of galaxy gas disks, concluding that galaxy gravity prevents RT instability in the inner disk but not in stripped gas.

Contribution

It clarifies the conditions under which RT instability can or cannot occur during ram pressure stripping in galaxies.

Findings

RT instability is unlikely in the galaxy's inner disk due to gravity.

Stripped gas may still be subject to RT instability.

Galaxy gravity prevents RT instability in the inner disk.

Abstract

Ram pressure stripping, i.e. the removal of a galaxy's gas disk due to its motion through the intracluster medium of a galaxy cluster, appears to be a common phenomenon. Not every galaxy, however, is completely stripped of its gas disk. If the ram pressure is insufficiently strong, only the outer parts of the gas disk are removed, and the inner gas disk is retained by the galaxy. One example of such a case is the Virgo spiral NGC 4402. Observations of NGC 4402 (Crowl et al. 2005) reveal structures at the leading edge of the gas disk, which resemble the characteristic finger-like structures produced by the Rayleigh-Taylor (RT) instability. We argue, however, that the RT instability is unlikely to be responsible for these structures. We demonstrate that the conditions under which a galaxy's disk gas experiences ram pressure stripping are identical to those that lead to RT instability. If the galaxy's gravity prevents ram pressure stripping of the inner disk, it also prevents the RT instability. In contrast, the stripped gas could still be subject to RT instability, and we discuss consequences for the stripped gas.