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R. A. M. Walterbos, J. F. Helmboldt (NMSU), G. D. Bothun (U. of Oregon), K. O'Neil (NAIC/Cornell)
A sample of ~120 galaxies was chosen from the H{\sc i} Parkes All Sky Survey (H{\sc i}PASS) to deduce details about star formation in nearby disk galaxies with no bias to optical surface brightness selection effects. Broad (B and R) and narrow band (H\alpha) photometry was obtained for 69 of these. The sample is dominated by late-type, dwarf disks (mostly Sc and Sm galaxies). For 69 of these H{\sc i}PASS galaxies, we measured the properties of the H{\sc ii} regions on H\alpha, continuum subtracted images, using the HIIphot package developed by Thilker et al (2000). All but one of the galaxies contained at least one detectable H{\sc ii} region. For each galaxy with sufficient objects, an H{\sc ii} region luminosity function (LF) was obtained. The LFs typically peak at a luminosity fainter than ~1038 ergs s-1 and extend out to 1039 ergs s-1 or brighter. About 65% of the galaxies contain at least one H{\sc ii} region with LH\alpha \ge1039 ergs s-1. When compared with H{\sc ii} region LF data for early-type spirals, the slopes for the LFs of this sample are typically more shallow and the fraction of galaxies with at least one luminous HII region is significantly higher. Comparison of the total H\alpha flux to that from the H{\sc ii} regions was used to estimated the amount of diffuse ionized gas (DIG) contained in each of these systems. A wide range of diffuse fractions was found; the typical value was similar to the values found for normal spirals.
The author(s) of this abstract have provided an email address for comments about the abstract: helmbold@nmsu.edu
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.