Wakes of ram-pressure-stripped disc galaxies

Spiral galaxies that move through the intracluster medium (ICM) lose a substantial amount of their gas discs due to ram-pressure stripping. The recent observations of NGC 4388 by Oosterloo & van Gorkom reveal a tail of stripped gas of similar to 100 kpc behind the source galaxy. We present first 3D hydrodynamical simulations of the evolution of such ram-pressure-stripped tails. We find that if the ICM wind does not vary significantly over a period of a few 100 Myr, subsonic galaxies produce a tail with regular features similar to a von Karman vortex street. In this case, the tail widens systematically by about 45 kpc per 100 kpc distance behind the source galaxy. The widening rate is independent of the galaxy's inclination for a large range of inclinations. For supersonic galaxies, the tail is more irregular than for subsonic ones. The tail observed for NGC 4388 is narrower than the tails in our simulations. Reasons for this difference may be a time-dependent ram pressure or additional physical processes such as heat conduction or viscosity. In addition, we conclude that the observed S-shape of this tail is not due to von Karman oscillations. Finally, we discuss implications for the distribution of metals in the ICM due to ram-pressure stipping.