HUBBLE-SPACE-TELESCOPE IMAGES OF THE NUCLEAR STAR-FORMING REGION IN THE INTERACTING GALAXY NGC-5930

High-resolution images of the spiral galaxy NGC 5930 have been obtained with the Planetary Camera aboard the Hubble Space Telescope in the emission lines of [O III] lambda lambda 4959, 5007 + H beta and H alpha + [N II] lambda lambda 6548, 6583, and their adjacent continua. NGC 5930 is the interacting companion of the Type 2 Seyfert galaxy NGC 5929. Five bright continuum knots, which probably represent star clusters, are found in the central similar or equal to 1 ''.5(200 h(-1) pc, h = H-0/100 km s(-1) Mpc(-1)). Four of these knots are associated with an elliptical ring of low-excitation gas with dimensions 2 '' 4 X 1 '' 6 (320 h(-1) X 220 h(-1) pc), while the fifth lies close to the ring's center. This gaseous ring, which probably lies in the plane of the disk, has an H-alpha luminosity approximate to 7 X 10(40) h(-2) ergs s(-1). Assuming that the initial mass function for 5-120 M, stars is represented by a power law with an exponent of -2.5, the H-alpha luminosity implies a modest star formation rate of 0.07 h(-2) M.. yr(-1) for 5-120 M. stars, and a supernova rate from the explosion ofmassive stars approximate to 3 X 10(-3) h(-2) yr(-1). This nuclear star forming region appears to be similar to other nuclear rings in spiral galaxies. It has often been argued that such nuclear rings form at or near the inner Lindblad resonance. If this is the case for NGC 5930, the small radius of the ring implies a strongly concentrated central mass distribution.