DETECTION OF INFALLING HYDROGEN IN TRANSFER BETWEEN THE INTERACTING GALAXIES NGC5426 AND NGC5427

摘要

Using velocity tagging we have detected hydrogen from NGC5426 falling onto its interacting partner NGC5427.Our observations, with the GHaFaS Fabry–Perot spectrometer, produced maps of the two galaxies in Ha surface brightness and radial velocity. We found emission with the range of velocities associated with NGC5426 along lines of sight apparently emanating from NGC5427, superposed on the velocity map of the latter. After excluding instrumental effects we assign the anomalous emission to gas pulled from NGC5426 during its passage close to NGC5427. Its distribution, more intense between the arms and just outside the disk of NGC5427, and weak, or absent, in the arms, suggests that the infalling gas is behind the disk, ionized by Lyman continuum photons escaping from NGC5427. Modeling this, we estimate the distances of these gas clouds behind the plane: a few hundred parsecs to a few kiloparsecs. We also estimate the mass of the infalling (ionized plus neutral) gas, finding an infall rate of 10M per year, consistent with the high measured star formation rate across the disk of NGC5427 and with the detected circumnuclear galactic wind.