AAS 203rd Meeting, January 2004
Session 115 Dwarf, Irregular and Starburst Galaxies
Poster, Thursday, January 8, 2004, 9:20am-4:00pm, Grand Hall

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[115.19] Star Formation Properties of Irregular Galaxies

D. A. Hunter (Lowell Observatory), B. G. Elmegreen (IBM T. J. Watson Research Center)

What regulates star formation in gas-rich dwarf galaxies on global and local scales? To address this question, we have conducted a survey of a large sample of reasonably normal, relatively nearby, non-interacting galaxies without spiral arms. The sample includes 94 Im galaxies, 26 Blue Compact Dwarfs, and 20 Sm systems. The data consist of UBV and H\alpha images for the entire sample, and JHK images, HI maps, CO observations, and HII region spectrophotometry for a sub-sample. The H\alpha, UBV, and JHK image sets act as probes of star formation on three different times scales: H\alpha images trace the most recent star formation (\leq10 Myrs) through the ionization of natal clouds by the short-lived massive stars; UBV, while a more complicated clue, integrates over the past Gyr; and JHK integrates over the lifetime of the galaxy where even in Im galaxies global JHK colors are characteristic of old stellar populations. These data are being used to determine the nature and distribution of the star formation activity, to characterize the interstellar medium out of which the clouds and stars are forming, and to develop models that describe the important processes that drive star formation in these tiny systems. Here we present the H\alpha data: integrated star formation rates, azimuthally-averaged H\alpha surface brightnesses, and extents of star formation, and explore the relationship of the star formation properties to other integrated parameters of the galaxies.

One TI CCD used in this work was provided to Lowell by the National Science Foundation and another was on loan from the U. S. Naval Observatory in Flagstaff. The H\alpha filters were purchased with funds provided by a Small Research Grant from the American Astronomical Society, National Science Foundation grant AST-9022046, and grant 960355 from JPL. Funding for carrying out this work was provided by the Lowell Research Fund and by the National Science Foundation through grants AST-0204922 to DAH and AST-0205097 to BGE.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.