Starburst galaxy NGC 7673: a minor merger remnant

We investigate the kinematics of the luminous starburst galaxy NGC 7673 = Mrk 325, a nearby example of a 'clumpy irregular galaxy'. Images with the WIYN 3.5m telescope reveal outer wisps associated with mergers, and we suggest NGC 7673 is the survivor of a minor merger. DensePak spectroscopy of the Ha kinematics shows that the H II regions are confined to a rotating disk. The Ha emission line velocity field indicates that although there is widespread star formation across the inner disk, it is still rotating smoothly. The Ha emission profiles over the brightest regions of the galaxy have two components: narrow, FWHM approximate to 50 km s(-1) lines, and broad, FWHM 150 km s(-1) lines. The width of the narrow lines is likely due to a combination of averaging effects, stellar winds and SNRs, and possibly gravitational motions within the disk. The origin of the broad component, which eclipses the narrow component in flux over much of the galaxy's inner regions, is still unclear. We may be looking at turbulent gas encased in bubbles carved out by massive stars and their descendants, or possibly some localized outflows from the disk.