Neutral hydrogen gas in interacting galaxies: the NGC 1511 galaxy group

We present Hi line and 20-cm radio continuum observations of the NGC 1511 galaxy group obtained with the Australia Telescope Compact Array. The data reveal an extended, rather disturbed Hi distribution for the peculiar starburst galaxy NGC 1511 and a narrow bridge to its small companion galaxy, NGC 1511B, which has been severely distorted by the interaction/collision between the two galaxies. No stellar counterpart to the gaseous bridge has been detected. In addition, we find that the peculiar optical ridge to the east of NGC 1511 is probably the stellar remnant of a galaxy completely disrupted by interactions with NGC 1511. The slightly more distant neighbour, NGC 1511A, shows a regular Hi velocity field and no obvious signs of interactions. Radio continuum emission from NGC 1511 reveals three prominent sources on top of a more diffuse, extended distribution. We derive an overall star formation rate of 7M⊙yr−1. The most enhanced star formation is found in the south-eastern part of the disc, coincident with several bright Hii regions, and closest to the peculiar optical ridge. No continuum emission was detected in the companions, but NGC 1511B appears to show an Hii region at its faint western edge, closest to NGC 1511. The group displays a prime example of interaction-induced star formation activity.