AAS 207th Meeting, 8-12 January 2006
Session 179 Evolution of Galaxies, and Galaxies Surveys at Low Redshift
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[179.22] ALFALFA Discovery of an HI Cloud Complex in the Virgo Cluster

R. Giovanelli, M.P. Haynes, B. Kent, A. Saintonge, S. Stierwalt (Cornell), N. Brosch (Wise Observatory), L.G. Hoffman (Lafayette), J. Rosenberg (CfA), B. Catinella, E. Momjian (NAIC)

A large complex of HI clouds was discovered in the course of the Spring 2005 observations of the ALFALFA survey (Giovanelli et al. 2005, AJ in press and astro-ph/0508301) at the Arecibo 305 m telescope. The complex extends about 40', at a mean heliocentric radial velocity of 500 km/s. It consists of several clumps, the largest of which is centered near 12:30:26+09:28:00 (2000). The overall HI mass of the sytem approches 109 solar, if a distance of 16 Mpc is assumed. No ordered velocity field is discernible. Most of the components of the system do not appear to be associated with optical counterparts, except for a cloud near 12:31:18+09:29:00, cz=606 km/s, which appears to be related with the galaxy VCC1357, a dI(?) of 0.2x0.1 arcmin. The galaxy NGC 4424, an SBa of 3.6x1.8 arcmin at cz=476 km/s, is located some 45' (210 kpc at the cluster distance) away from the center of the cloud complex and it exhibits a disturbed HI disk (Cortes, Kenney and Hardy 2005, preprint). Morphology and velocity fields do not suggest a tidal origin for the system. Interpretation in terms of a galaxy harassment scenario in the cluster potential appears more likely. Structural details of the central region of the complex are shown in the VLA HI synthesis images presented in the companion paper by Spekkens et al. (2006). This research is partially supported by NSF/AST-0307661 NSF/AST-0435697 and a Brinson Foundation grant.

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