2008/06/19 by Brian R. Kent, Riccardo Giovanelli, Martha P. Haynes +6
Physics and Astronomy · #Astronomy and Astrophysical Research #Centroid #Galaxies: Formation, Evolution, Phenomena #Galaxy #Milky Way #Redshift #Sky #Stellar, planetary, and galactic studies #Telescope #Virgo Cluster #William Herschel Telescope #astro-ph
paper · pdf · doi:10.1088/0004-6256/136/2/713
25 pages, 1 Table, 8 figures, Accepted by the Astronomical Journal
arxiv created 2008/06/19 · openalex publication_date 2008/07/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present the third installment of HI sources extracted from the Arecibo Legacy Fast ALFA extragalactic survey. This data set continues the work of the Virgo ALFALFA catalog. The catalogs and spectra published here consist of data obtained during the 2005 and 2006 observing sessions of the survey. The catalog consists of 578 HI detections within the range 11 h 36 m < right ascension (R.A.)(J2000) <13 h 52 m and +08° < declination (decl.)(J2000) <+12°, and cz ☉ < 18, 000 km s −1 . The catalog entries are matched with optical counterparts where possible through the examination of digitized optical images. The catalog detections can be classified into three categories: (a) detections of high reliability with a signal-to-noise ratio (S/N) > 6.5; (b) high-velocity clouds in the Milky Way or its periphery; and (c) signals of lower S/N which coincide spatially with an optical object and known redshift. 75% of the sources are newly published HI detections. Of particular note is a complex of HI clouds projected between M87 and M49 that do not coincide with any optical counterparts. Candidate objects without optical counterparts are few. The median redshift for this sample is 6500 km s −1 and the cz distribution exhibits the local large-scale structure consisting of Virgo and the background void and the A1367-Coma supercluster regime at cz ☉ ∼ 7000 km s −1 . Position corrections for telescope pointing errors are applied to the data set by comparing the ALFALFA continuum centroid with those cataloged in the NRAO VLA 7 Sky Survey (NVSS). The uncorrected positional accuracy averages 27''(21'' median) for all sources with S/N > 6.5 and is of order ∼21''(16'' median) for signals with S/N > 12. Uncertainties in distances toward the Virgo cluster can affect the calculated HI mass distribution.