Discovery of a Large-scale H i Plume in the NGC 7194 Group

Abstract

We present the discovery of a new H i structure in the NGC 7194 group from the observations using the Karl G. Jansky Very Large Array. NGC 7194 group is a nearby ( z ∼ 0.027) small galaxy group with five quiescent members. The observations reveal a 200 kpc long H i plume that spans the entire group with a total mass of M _H I = 3.4 × 10 ^10 M _⊙ . The line-of-sight velocity of the H i gas gradually increases from south (7200 km s ^−1 ) to north (8200 km s ^−1 ), and the local velocity dispersion is up to 70 km s ^−1 . The structure is not spatially coincident with any member galaxies but it shows close associations with a number of blue star-forming knots. Intragroup H i gas is not rare, but this particular structure is still one of the unusual cases in the sense that it does not show any clear connection with sizable galaxies in the group. We discuss the potential origins of this large-scale H i gas in the NGC 7194 group and its relation with the intergalactic star-forming knots. We propose that this H i feature could have originated from tidal interactions among group members or the infall of a late-type galaxy into the group. Alternatively, it might be leftover gas from flyby intruders.

Keywords

• Neutral hydrogen clouds
• Galaxy groups
• Star forming regions