The 2D velocity field of NGC 1084 obtained with the scanning Fabry-Perot interferometer tuned at the redshifted and [NII] emission lines has revealed an extended region in the NE part of the galaxy where two kinematically distinct gas systems are present. The first system is related to normally rotating gas, whereas the second one reveals line-of-sight velocities differing by . The "spur" covers a region of kpc in size and avoids the bright HII regions. The fast-moving gas is mostly characterized by enhanced [NII]6583 emission, which evidences for the presence of strong shock waves. Possible explanations for this phenomenon are the infall of extraplanar high-velocity clouds or the tidal disruption and accretion of another small galaxy.
© European Southern Observatory (ESO) 2000
Online publication: December 5, 2000