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

TL;DR

This study reports the discovery of a significant amount of atomic gas far from NGC 4388, linking it to extended ionized gas features and suggesting ram pressure stripping as a key process in galaxy environment interactions.

Contribution

It provides observational evidence and numerical modeling of ram pressure stripping effects on atomic gas and star formation in the Virgo cluster galaxy NGC 4388.

Findings

Detected 6 x 10^7 solar masses of atomic gas beyond 20 kpc from NGC 4388.

Numerical simulations support ram pressure stripping as the origin of the gas and Hα plume.

Identified a star-forming gas cloud likely falling back onto the galaxy.

Abstract

We have discovered 6 10^7 M_{\odot} of atomic gas at a projected distance greater than 4' (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.