The Arecibo Legacy Fast ALFA Survey. III. HiSource Catalog of the Northern Virgo Cluster Region

Abstract

We present the first 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 filtering technique and then examined interactively to yield global HI parameters. A total of 730 HI detections are catalogued within the solid angle 11 h 44 m < R.A.(J2000) < 14 h 00 m and +12 • < Dec.(J2000) < +16 • , and redshift range −1600 km s −1 < cz < 18000 km s −1 . 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 Milky Way or its periphery; and (c) signals of lower S/N (to ∼ 4.5) which coincide spatially with an optical object of known similar redshift. Although this region of the sky has been heavily surveyed by previous targeted observations based on optical flux-or size-limited samples, 69% of the extracted sources are newly reported HI detections. The resultant positional accuracy of HI sources is dependent on S/N: it averages 24 ′′ (20 ′′ median) for all sources with S/N > 6.5 and is of order ∼17 ′′ (14 ′′ median) for signals with S/N > 12. The median redshift of the sample is ∼7000 km s −1 and its distribution reflects the known local large scale structure including the Virgo cluster and the void behind it, the A1367-Coma supercluster at cz ∼7000 km s −1 and a third more distant overdensity at cz ∼13000 km s −1 . Distance uncertainties in and around the Virgo cluster perturb the derived HI mass distribution. Specifically, an apparent deficiency of the lowest HI mass objects can be attributed, at least in part, to the incorrect assignment of some foreground objects to the cluster distance. Several extended HI features are found in the vicinity of the Virgo cluster. A small percentage (6%) of HI detections have no identifiable optical counterpart, more than half of which are high velocity clouds in the Milky Way vicinity; the remaining 17 objects do not appear connected to or associated with any known galaxy. Based on these initial results, ALFALFA is expected to fulfill, and even exceed, its predicted performance objectives in terms of the number and quality of HI detections.

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

“…Single-dish Hi 21 cm line emission data, necessary for quantifying the Hi content of galaxies, were taken from Gavazzi et al (2003), Springob et al (2005), Giovanelli et al (2007), Kent et al (2008) and NED. Estimates of atomic hydrogen mass or upper limits are available for ∼97% (252/260) of the late-type galaxies.…”

TheHerschelVirgo Cluster Survey

“…To derive D, we used neutral hydrogen masses available from the ALFALFA catalog (Giovanelli et al 2007;Kent et al 2008, see Table 1). The angular resolution of the 21-cm data (3.…”

TheHerschelVirgo Cluster Survey

“…In particular, the ISM in the immediate surroundings of M87 can be traced by dust emission, as strong radio continuum emission considerably reduces the ALFALFA Hi detection sensitivity within 1 • of M87 (Giovanelli et al 2007). To date, the Andromeda satellites NGC 205 and NGC 185 are the only dEs that have been detected in the far-infrared (Haas 1998;Marleau et al 2006Marleau et al , 2009.…”