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| Paper: |
Starbursts in the Far-Ultraviolet |
| Volume: |
348, Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE |
| Page: |
467 |
| Authors: |
Heckman, T.M. |
| Abstract: |
Starbursts are a significant component of the present-day universe, and offer unique laboratories for studying the processes that have regulated the formation and evolution of galaxies and the intergalactic medium. The combination of large aperture size, medium-to-high spectral resolution, and access to the feature-rich far-ultraviolet band make FUSE a uniquely valuable tool for studying starbursts. In this paper, I summarize several of FUSE's “greatest hits” for starbursts. FUSE observations of the strong interstellar absorption lines show that powerful starbursts drive bulk outflows of the neutral, warm, and coronal phases of the ISM with velocities of several hundred km/s. These are similar to the outflows seen in Lyman Break Galaxies at high redshift. The weakness of OVI emission associated with these flows implies that radiative cooling by coronal gas is not energetically significant. This increases the likelihood that the flows can eventually escape the galaxies and heat and enrich the intergalactic medium. FUSE observations show that local starburst galaxies are quite opaque below the Lyman edge, with typically no more than ∼6% of the ionizing photons escaping (even in starbursts with strong galactic winds). This has potentially important implications for the role of star forming galaxies in the early reionization of the universe. FUSE observations of molecular hydrogen in starbursts show very low molecular gas fractions in the translucent ISM (even in starbursts where mm-wave data show that the ISM is primarily molecular). This implies that the molecular gas is all in dense clouds that are completely opaque in the far-UV. The high far-UV intensity in starbursts photodissociates molecular hydrogen in the diffuse ISM. Finally, FUSE observations of chemical abundances in the neutral ISM in dwarf starburst galaxies suggest that the metallicity in the HI (which dominates the baryonic mass budget) may be systematically lower than in the HII regions. This would have important implications for galactic chemical evolution. |
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