Panchromatic study of nearby ultraviolet-bright starburst galaxies: Implications for massive star formation and high-redshift galaxies

We present a panchromatic study of nearby starburst galaxies from the ultraviolet to the visible, including narrowband H alpha using Wisconsin-Indiana-Yale-NOAO (WIYN) and Hubble Space Telescope data, to determine how star formation processes affect the morphologies and integrated fluxes of nearby starbursts. We find that the UV and H alpha morphologies of starbursts tend to differ, although not in a standard or predictable manner. From our sample of six nearby starbursts, three systems show good correlations between UV and H alpha fluxes, but we find differences in UV and H alpha morphology among the other three. Occasionally we find systems with well-defined H II regions without the corresponding brightness in the UV, and vice versa. We discuss the likely mechanisms behind these differences, which include starburst ages, dust absorption, stellar energy ejecta through supernovae and winds, and leakage of UV photons from stellar clusters. We conclude that the large-scale morphological features in starbursts are primarily due to both age and absorption from a picket-fence dust distribution. We further demonstrate the similarity and differences between these nearby starbursts and high-redshift star-forming galaxies. The overall morphology of our sample of starbursts changes little between UV and visible wavelengths. If high-redshift galaxies are similar to these starbursts, their morphologies should change little between rest-frame UV and optical. We also show that FIR and UV spectral energy distributions and slopes can be used to determine large-scale morphological features for extreme starbursts, with the steepest FIR slopes correlating with the most disturbed galaxies.