H alpha 3: an H alpha imaging survey of HI selected galaxies from ALFALFA: I. Catalogue in the Local Supercluster

The authors present H alpha 3, an H alpha narrow-band imaging survey of similar to 400 galaxies selected from the H I Arecibo Legacy Fast ALFA Survey in the Local Supercluster, including the Virgo cluster. By using hydrogen recombination lines as a tracer of recent star formation, the authors aim to investigate the relationships between atomic neutral gas and newly formed stars in different environments, morphological types, and over a wide range of stellar masses. This survey provides a complete census of the star formation in H I rich galaxies of the local universe. The authors present the properties of the galaxy sample, together with H alpha fluxes and equivalent widths. They find an excellent agreement between the fluxes determined from our images in apertures of 3 arcsec diameter and the fluxes derived from the SDSS spectral database. From the H alpha fluxes corrected for galactic and internal extinction and for N II contamination they derive the global star formation rates.