The Arecibo Legacy Fast ALFA Survey. III. H I Source Catalog of the Northern Virgo Cluster Region

We present the rst installment of HI sources extracted from the Arecibo Legacy Fast ALFA (ALFALFA) extragalactic survey, initiated in 2005. Sources have been extracted from 3-D spectral data cubes exploiting a matched ltering technique and then examined interactively to yield global HI parameters. A total of 730 HI detections are catalogued within the solid angle 11h44m < R.A.(J2000) < 14h00m and +12 < Dec.(J2000) < +16, and redshift range 1600 km s1 < cz < 18000 km s1. In comparison, the HI Parkes All-Sky Survey (HIPASS) detected 40 HI signals in the same region. Optical counterparts are assigned via examination of digital optical imaging databases. ALFALFA HI detections are reported for three distinct classes of signals: (a) detections, typically with S/N> 6.5; (b) high velocity clouds in the Milk