Making Hay with ALFALFA: The Star-Formation Properites of an HI-selected Sample of Galaxies

We are requesting time to complete an extensive project of narrow- band H(alpha) imaging. Our primary goal is to derive the most accurate value possible for the local star-formation rate (SFR) density. Our target sample is drawn from ALFALFA, a blind HI survey being carried out using the Arecibo 305-m radio telescope. We argue that this HI-selected sample provides the best available catalog of sources that could be used for measuring the SFR density because it detects all galaxies capable of making stars and is quite comprehensive. The current proposal builds upon our ongoing H(alpha) imaging project executed on both the KPNO 2.1- m and WIYN 0.9-m telescopes. The better light grasp and resolution of the KPNO 2.1-m is needed for the more distant galaxies in our volume. Our new observations will be combined with the images from our ongoing narrow-band project and will complete one of the largest, most comprehensive samples of H(alpha) images available (>1500). We will also use the survey data to explore a number of additional science topics, such as modes of star formation in galaxies, the impact of large- scale environment on star formation, and the properties of point-like emission sources in our survey fields.