HI OBSERVATIONS OF SOUTHERN EXTREME LATE-TYPE GALAXIES .1. AN OPTICALLY FAINT SAMPLE

We have made neutral hydrogen (H I) 21 cm line observations of a sample of 90 southern, low luminosity, extreme late-type galaxies using the 140 ft (43 m) radio telescope at the National Radio Astronomy Observatory. Our targets were selected from catalogs derived from deep photographic exposures taken with Schmidt telescopes. Since our goal was to increase the completeness of samples of small, gas-rich galaxies within the Local Supercluster, our search for H I emission extended out to radial velocities of 3000 km s-1. Our sample has a mean MHI, three times lower than reported for brighter extreme late-type galaxies in the same region of the sky. We find that the observed MHI in our sample increases with redshift, indicating that the sample of small, gas-rich galaxies within the Local Supercluster remains incomplete. We briefly comment on some of the implications of our observations in terms of the H I properties and H I luminosity function of extreme late-type field galaxies and on the locations of such objects within previously cataloged groups of galaxies.