Discovery of a giant HI tail in the galaxy group HCG 44

TL;DR

This paper reports the discovery of a giant HI tail in galaxy group HCG 44, providing direct evidence of gas stripping and emphasizing the importance of deep HI observations for understanding galaxy interactions.

Contribution

The discovery of a large HI tail in HCG 44 offers new observational evidence of gas stripping in galaxy groups, highlighting the need for extensive HI surveys.

Findings

The HI tail is approximately 300 kpc long and contains about 5x10^8 solar masses of HI.

No diffuse stellar light was detected at the tail's location down to a magnitude limit of 28.5 mag/arcsec^2.

The tail likely formed from gas stripped from NGC 3187 or as a result of an interaction with NGC 3162.

Abstract

We report the discovery of a giant HI tail in the intra-group medium of HCG 44 as part of the Atlas3D survey. The tail is ~300 kpc long in projection and contains ~5x10^8 M_sun of HI. We detect no diffuse stellar light at the location of the tail down to ~28.5 mag/arcsec^2 in g band. We speculate that the tail might have formed as gas was stripped from the outer regions of NGC 3187 (a member of HCG 44) by the group tidal field. In this case, a simple model indicates that about 1/3 of the galaxy's HI was stripped during a time interval of <1 Gyr. Alternatively, the tail may be the remnant of an interaction between HCG 44 and NGC 3162, a spiral galaxy now ~650 kpc away from the group. Regardless of the precise formation mechanism, the detected HI tail shows for the first time direct evidence of gas stripping in HCG 44. It also highlights that deep HI observations over a large field are needed to gather a complete census of this kind of events in the local Universe.