Em. Moore et St. Gottesman, A NEUTRAL HYDROGEN STUDY OF THE BARRED SPIRAL GALAXY NGC-3319, Monthly Notices of the Royal Astronomical Society, 294(3), 1998, pp. 353-372
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).