Strong non-circular motions of gas in the spiral galaxy NGC 1084

Abstract

The results of $H_α$ and [NII]$λ6583$ observations of the spiral galaxy NGC 1084 at the SAO 6m telescope with a Fabry-Perot interferometer are presented. The complex structure of the emission line profile has revealed the presence of giant star formation regions (``spur'') in the NE part of the galaxy. In this region the $H_α$ line shows two distinct components, with line-of-sight velocity differences of $\pm(100-150)\km$. The first component corresponds to normal circular rotation. The second velocity component may be a signature of non-circular motions of the ionized gas in shock wave fronts. An increase of the ${[NII]}/H_α$ line ratio confirms the shock wave interpretation of these features. The ionized gas kinematics in this galaxy is discussed.