Detection of infalling hydrogen in transfer between the interacting
  galaxies NGC 5426 and NGC 5427
  Using velocity tagging we have detected hydrogen from NGC 5426 falling onto
its interacting partner NGC 5427. Our observations, with the GHaFaS Fabry-Perot
spectrometer, produced maps of the two galaxies in Halpha surface brightness
and radial velocity. We found emission with the range of velocities associated
with NGC 5426 along lines of sight apparently emanating from NGC 5427,
superposed on the velocity map of the latter. After excluding instrumental
effects we assign the anomalous emission to gas pulled from NGC 5426 during its
passage close to NGC 5427. Its distribution, more intense between the arms and
just outside the disk of NGC 5427, and weak, or absent, in the arms, suggests
that the infalling gas is behind the disk., ionized by Lyman continuum photons
escaping from NGC 5427. Modeling this, we estimate the distances of these gas
clouds- behind the plane: a few hundred pc to a few kpc. We also estimate the
mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10
solar masses per year, consistent with the high measured SFR across the disk of
NGC 5427 and with the detected circumnuclear galactic wind.
