Galaxies 09: Assembly, Gas Content and Star Formation History of Galaxies
Stacy McGaugh
University of Maryland
Star Formation in Gas Rich Low Surface Brightness Galaxies
The gas mass fraction of spiral galaxies is correlated with both luminosity and surface brightness.
For the dimmest galaxies, it is not uncommon for the gas to outweigh the stars, and gas fractions can exceed 90\% in the most extreme cases. Using H$\alpha$ as a star formation tracer, we find that while the absolute star formation rates are low ($<$ 0.1 M$_{\odot}$/yr), the stellar birthrates are typically high (b $>$ 2). It is not clear what the star formation history of these galaxies is, nor how star formation proceeds at all in these extreme environments which, being low metallicity and gas rich, may be our best local analogs to conditions at high redshift. To date, essentially all of the observed gas is in the atomic phase; how much molecular gas is present, and how it comes and goes, is an open question begging for future facilities such as ALMA.
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