Virgo Galaxies with Long One-sided H i Tails

In a new HI imaging survey of Virgo galaxies (VIVA: VLA Imaging of Virgogalaxies in Atomic gas), we find 7 spiral galaxies with long HI tails. Themorphology varies but all the tails are extended well beyond the optical radiion one side. These galaxies are found in intermediate-low density regions(0.6-1 Mpc in projection from M87). The tails are all pointing roughly awayfrom M87, suggesting that these tails may have been created by a global clustermechanism. While the tidal effects of the cluster potential are too small, arough estimate suggests that simple ram-pressure stripping indeed could haveformed the tails in all but two cases. At least three systems show HItruncation to within the stellar disk, providing evidence for a gas-gasinteraction. Although most of these galaxies do not appear disturbed optically,some have close neighbors, suggesting that tidal interactions may have movedgas outwards making it more susceptible to the ICM ram-pressure or viscosity.Indeed, a simulation study of one of the tail galaxies, NGC 4654, suggests thatthe galaxy is most likely affected by the combined effect of a gravitationalinteraction and ram-pressure stripping. We conclude that these one-sided HItail galaxies have recently arrived in the cluster, falling in on highly radialorbits. It appears that galaxies begin to lose their gas already atintermediate distances from the cluster center through ram-pressure orturbulent viscous stripping and tidal interactions with neighbours, or acombination of both.