AAS 207th Meeting, 8-12 January 2006
Session 89 Dwarf Galaxies: Stellar Distributions and Star Formation
Oral, Tuesday, 10:00-11:30am, January 10, 2006, Salon 3

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[89.04] Predominant Modes of Global Star Formation in Dwarf Galaxies

J. Lee (University of Arizona)

An outstanding question in extragalactic studies of the local universe is whether the recent star formation histories of low mass galaxies are dominated by global starbursts or modes that are more quiescent and continuous. Using H\alpha-derived star formation rates and birthrate parameters of a nearly volume-limited sample of ~400 galaxies within 11 Mpc (11HUGS - 11 Mpc H\alpha UV Galaxy Survey), I present results that statistically constrain the predominant modes of star formation in present-day dwarf galaxies. The results of my studies paint a picture in which dwarfs that are currently experiencing massive global bursts are just the ~5% tip of a low-mass galaxy iceberg. Moreover, bursts are responsible for 15-20% of the total star formation in the overall dwarf population, so the majority of stars in low-mass systems are not formed in this mode today. The data also show an intriguing suggestion of bi-modality in the recent star formation histories of dwarfs, with 85% of the population exhibiting log-normally distributed birthrates (continuous SF) and 15% having excessively high or low birthrates compared with the main distribuion (burst and post-burst systems). Future science with incoming GALEX UV data will also be highlighted.

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