Atomic gas far away from the Virgo cluster core galaxy NGC 4388 A possible link to isolated star formation in the Virgo cluster?

We have discovered 6\10^7 M(odot) of atomic gas at a projected distance greater than 4 ʹ (20 kpc) from the highly inclined Virgo spiral galaxy NGC 4388. This gas is most probably connected to the very extended H (alpha) plume detected by Yoshida et al. (2002). Its mass makes a nuclear outflow and its radial velocity a minor merger as the origin of the atomic and ionized gas very unlikely. A numerical ram pressure simulation can account for the observed HI spectrum and the morphology of the H (alpha) plume. An additional outflow mechanism is still needed to reproduce the velocity field of the inner H (alpha) plume. The extraplanar compact HII region recently found by Gerhard et al. (2002) can be explained as a stripped gas cloud that collapsed and decoupled from the ram pressure wind due to its increased surface density. The star-forming cloud is now falling back onto the galaxy.