Morphology and Stellar Content of the Starburst Regions in Wolf-Rayet Galaxies

Previous abstract Next abstract

Session 37 -- Massive Hot Stars with the Hubble Space Telescope Part II
Oral presentation, Tuesday, 31, 1994, 2:00-5:30

[37.04] Morphology and Stellar Content of the Starburst Regions in Wolf-Rayet Galaxies

William D. Vacca (UC Berkeley)

Wolf-Rayet galaxies are a subset of H {\sc ii} galaxies whose integrated spectra exhibit broad stellar emission lines due to the presence of hundreds to thousands of Wolf-Rayet stars. These galaxies exhibit a number of other spectral properties indicative of a large ``starburst'' population of young, hot, massive stars. We have obtained ground-based optical and HST FOC ultraviolet images of several Wolf-Rayet galaxies and will present examples of the spatial morphologies observed at these wavelengths. Large star-forming regions which appear to be single units in the optical images are resolved into numerous discrete compact bright knots in the HST ultraviolet images. These starburst knots are typically less than $100$ pc in size and generally too small and closely spaced to be detected individually in the ground-based optical images. Ultraviolet photometry determined from the HST images, as well as ground-based optical spectroscopy, of the starburst regions indicate, however, that the knots contain large numbers of hot (O, B, and Wolf-Rayet) stars and are typically several times more luminous than 30 Doradus, the giant H {\sc ii} region in the LMC. The intense bursts of star formation in these knots probably occurred only a few Myr ago and lasted less than about 1 Myr. Based on their sizes and estimated masses, we suggest that the starburst knots in these Wolf-Rayet galaxies may be proto-globular clusters which were formed during vigorous star formation episodes triggered by recent galaxy-galaxy mergers and/or interactions.

Tuesday program listing