AAS 198th Meeting, June 2001
Session 79. Galaxy Surveys
Oral, Thursday, June 7, 2001, 10:00-11:30am, C106

## [79.03] Star Formation Properties of HIPASS Galaxies I: Sample Characteristics

J. F. Helmboldt, R. A. M. Walterbos (New Mexico State University), G. D. Bothun (University of Oregon), W. J. G. de Blok (Australia National Telescope Facility), K. O'Neil (Arecibo Observatory)

Any sample of galaxies selected according to optical properties will be biased by the night sky towards higher surface brightness. This implies that so called low surface brightness (LSB) galaxies are under represented in many studies. This is of some concern when trying to understand the star formation properties of a given sample since LSB galaxies appear to have significantly different star formation histories that HSB galaxies. A sample of ~120 galaxies was chosen from the H{\sc i} Parkes All Sky Survey (H{\sc i}PASS) to be imaged in B and R band and in H\alpha to deduce details about star formation in nearby disk galaxies while avoiding such surface brightness selection effects. ~65 of these H{\sc i}PASS galaxies have been imaged in all three bandpasses for this paper. The sample is dominated by late-type, dwarf disks (mostly Sc and Sm galaxies) with exponential disk scalelengths around 1 kpc or less. They inhabit a range in colors over all values of central surface brightness and exhibit a weak trend between H\alpha flux per unit area and B-band surface brightness. H{\sc ii} regions were detected in all but one of the galaxies; many galaxies had as few as 2-5 which is what would be expected for a large sample of late-type galaxies. Calculation of the star formation rates (SFRs) using the integrated H\alpha luminosities shows that most of the galaxies have SFRs ~0.01-0.1 M\odot yr-1, which is typical for LSB and dwarf galaxies. It should be noted that such low SFRs cannot produce the amount of stars typically observed in such systems, implying that the SFRs were higher at some point in the past.