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D. Maoz (Tel-Aviv U. and Columbia U.), A.J. Barth (CfA), L.C. Ho (Carnegie Inst. of Washington), A. Sternberg (Tel-Aviv U.), A.V. Filippenko (UC Berkeley)
We present broad-band (U, V, I, and H) and narrow-band (H\alpha+[N~II] and Pa\alpha) images of the circumnuclear starburst rings in two nearby spiral galaxies, NGC~1512 and NGC~5248, obtained with the WFPC2 and NICMOS cameras on HST. Combined with previously published HST images at 2300 Å, these data provide a particularly wide wavelength range with which to study the properties of the stellar populations, the gas, and the dust in the rings. We examine the morphology, the line emission, the ionizing photon budget, and the extinction of the gas in the H~II regions. We identify the major (about 500 in each galaxy) compact continuum sources (super star clusters and individual stars), measure their spectral energy distributions from 0.2~\mum to 1.6~\mum, and compare them to spectral synthesis models to determine ages and extinctions. Most of the luminous sources (MV\approx -10 to -12 mag) are super star clusters that are blue, a few million years old, and not highly reddened. The starburst in each ring thus appears be a brief and well-synchronized event.
The author(s) of this abstract have provided an email address for comments about the abstract: dani@astro.columbia.edu