Kinematics and Structure of the Starburst Galaxy NGC 7673

The morphology and kinematics of the luminous blue starburst galaxy NGC 7673are explored using the WIYN 3.5m telescope. Signs of a past kinematicdisturbance are detected in the outer galaxy; the most notable feature is aluminous ripple located 1.55 arc minutes from the center of NGC 7673. Sub-arcsecond imaging in B and R filters also reveals red dust lanes and blue starclusters that delineate spiral arms in the bright inner disk and narrow bandHalpha imaging shows that the luminous star clusters are associated with giantH II regions. The Halpha kinematics measured with echelle imaging spectroscopyusing the WIYN DensePak fiber array imply that these HII regions are confinedto a smoothly rotating disk. The velocity dispersion in ionized gas in the diskis approximately 24 km/s, which sets an upper bound on the dispersion of youngstellar populations. Broad emission components with velocity dispersion approx.63 km/s are found in some regions are likely produced by mechanical powersupplied by massive, young stars; a violent starburst is occurring in akinematically calm disk. Although the asymmetric outer features point to amerger or interaction as the starburst trigger, the inner disk structureconstrains the strength of the event to the scale of a minor merger or weakinteraction that occurred at least an outer disk dynamical time scale in thepast.Comment: 16 pages, 7 figures, to appear in the September 1, 1999 issue of the Astrophysical Journa