Motions of the stars and the excited gas in the barred spiral galaxy NGC 3351

Abstract

The velocity field of the spiral-arm region of the bright barred spiral NGC 3351 has been determined from measurements of emission lines on spectra from the 4 meter Mayall telescope. The stellar velocity field of the bar also has been obtained by measurement of relatively sharp absorption features; the sharpness of the absorption lines is due to the small velocity dispersion along the line of sight, a = 140 + 30 km i The bar is rotating with a constant angular velocity of 80 + 20 km 1 kpc -1 and therefore is a quasi-stationary feature of the galaxy. There is no evidence for excited gas in the bar. Beyond the region of the bar, the velocities of the H ii regions in the spiral arms are consistent with a pattern of circular motion only, with the rotation curve reaching a maximum of Vrot 220 km 1 at R 3-5 kpc and decreasing to Vrot 170 km 1 at R 8 kpc. Noncircular motions have, however, been observed in the nuclear regions of NGC 3351. The kinematical major axis is the same as the line of nodes determined from the apparent ellipse formed by the projection of the galaxy on the plane of the sky. The systematic velocity of the galaxy is 779 + 3 km s -1, both from optical and from 21 cm neutral hydrogen data. Subject headings: galaxies: individual galaxies: internal motions stars: stellar dynamics