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G.R. Meurer, D.J. Hanish (The Johns Hopkins University), SINGG Team
We present the star formation properties of 92 HI selected galaxies observed in H\alpha and the R continuum for the Survey of Ionization in Neutral Gas Galaxies (SINGG). We show that the SINGG observations are more sensitive to low equivalent width and low surface brightness systems than prism emission line surveys and the Sloan Digital Sky Survey, respectively. A total of 110 emission line galaxies are observed in the 92 targets, with only one HI target not detected in H\alpha, indicating that gas rich dormant systems are exceedingly rare in the local universe. Distance independent normalized star formation indicators are compared - the star formation intensity (surface brightness), H\alpha equivalent width, and the gas cycling time. These correlate in the expected sense - higher star formation intensity corresponds to a larger equivalent width and a shorter gas cycling time. The star formation indicators have a larger scatter about the mean for dwarf galaxies compared to normal galaxies, in agreement with expectations from the Stochastic Self-Propagating Star Formation (SSPSF) scenario. However, the lack of significant numbers of non-detections is contrary to the expectations of SSPSF models. Star formation intensity increases and gas cycling time decreases with increasing R band effective surface brightness, while the dispersion in these quantities increases with R band intensity. These correlations may stem from a star formation law dependent on both the stellar and total mass surface densities, and is consistent with predictions from recent hierarchical assembly models.
Partial financial support for the work presented here was obtained from NASA grant NAG5-13083 (LTSA program) to G.R.\ Meurer.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.