| Abstract | The Arecibo Dual-Beam Survey is a ``blind'' 21 cm search for galaxies covering ~430 deg2 of sky. We present the data from the detection survey as well as from the follow-up observations to confirm detections and improve positions and flux measurements. We find 265 galaxies, many of which are extremely low surface brightness. Some of these previously uncataloged galaxies lie within the zone of avoidance, where they are obscured by the gas and dust in our Galaxy. Eighty-one of these sources are not previously cataloged optically, and there are 11 galaxies that have no associated optical counterpart or are only tentatively associated with faint wisps of nebulosity on the Digitized Sky Survey images. We discuss the properties of the survey, and in particular we make direct determinations of the completeness and reliability of the sample. The behavior of the completeness and its dependencies is essential for determining the H I mass function. We leave the discussion of the mass function for a later paper, but do note that we find many low surface brightness galaxies and seven sources with MHI<108 Msolar. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under cooperative agreement with the National Science Foundation. in Puerto Rico. |
