The physical properties of low redshift star forming galaxies: Insights from the space-UV and 20,000 SDSS spectra

We use ultraviolet (UV) and optical spectroscopy to study the physical properties of actively star forming galaxies. We have compiled an atlas of 46 rest frame UV spectra of 28 local starbursts which were observed with the FOS and GHRS instruments on board the Hubble Space Telescope (HST). We compare the HST data with lower resolution IUE data of the same galaxies and find systematic differences: the bright star clusters targeted in HST's ∼ 1″ apertures provide about 15% of the starburst luminosity traced by IUE's 10″ × 20″ aperture; they are bluer and have stronger stellar features, suggesting that the HST apertures have been preferentially placed on the youngest pieces of the burst. In contrast, lines arising from the interstellar medium (ISM) show similar equivalent widths in both large and small aperture observations, suggesting that the ISM is fairly homogeneous. We take advantage of the superior resolution of the HST spectra (a few 100 km s−1) to examine trends in UV spectral morphology with global galaxy properties. We develop a set of UV line indices to characterize the stellar wind and ISM absorption lines, and we examine correlations between these indices and a number of galaxy physical properties which are derived from available multi-wavelength data. We find strong correlations between strength of the far-UV ISM lines and the bolometric luminosity of the starburst, suggesting a turbulent origin for the line widths.; We undertook a more in depth investigation of the differences between star clusters and their surroundings using a longslit spectrum of the starburst galaxy NGC 5253 obtained with the Space Telescope Imaging Spectrograph . We extracted spectra from cluster and ‘field’ regions along the slit, and found the field to be devoid of O-stars.; We examine the relationship between stellar mass and metallicity in a sample of 30,000 galaxies with optical photometric and spectroscopic data available from the Sloan Digital Sky Survey. (Abstract shortened by UMI.)...