A NEUTRAL HYDROGEN STUDY OF THE BARRED SPIRAL GALAXY NGC-3319

Neutral hydrogen line observations of the late-type barred spiral gala xy NGC 3319 are presented. The distribution and kinematics of the gala xy are studied using the Very Large Array,(1) with spatial resolutions between 11 and 50 arcsec, and a channel separation of 10.33 km s(-1). As is typical for late-type galaxies, NGC 3319 is rich in H I, with a gaseous bar and spiral features. Several large, low-density regions a re present, and the Hr spiral structure is distorted, especially in th e south. The gas distribution is asymmetric and extends significantly further to the south-east due to a long, off-centre tail. Non-circular motions caused by the bar, spiral structure and low-density regions a re present in the radial velocity field, complicating the rotation cur ve analysis. These non-axisymmetric structures cause the values of the position angle and inclination derived from the velocity field to var y across the disc. In addition, beyond a radius of 180 arcsec, the vel ocity field is severely perturbed on the approaching (southern) side o f the galaxy, and the disc becomes non-planar. However, the galaxy doe s not show the typical 'integral sign' shape of a warped system. We de tect a small system approximately 11 arcmin (40 kpc) south of the cent re of NGC 3319. It is seen in eight velocity channels and is coinciden t with a small, resolved object in the Palomar Sky Survey. A tidal int eraction between this object and NGC 3319 is the most likely cause of the distorted spiral structure, the H I tail, and the velocity perturb ations found in the southern half of the galaxy. Infalling tidal debri s from such an event may account for the large, low-density regions fo und in the disc, several of which show kinematic evidence that suggest they are expanding superstructures. We are unable to determine the co rotation radius from the H I velocity field using kinematic methods, b ut a break in the slope of the abundance gradient places it near the e nd of the bar. Star formation zones, as determined from an H image of the galaxy, are aligned with H I peaks and, except in the outermost op tical disc, occur when the local H I density is in excess of 1.5 x 10( 21) cm(-2).