On the neutral gas content and environment of NGC 3109 and the Antlia dwarf galaxy

As part of a continuing survey of nearby galaxies, we have mapped the neutr al gas content of the low surface brightness Magellanic-type galaxy NGC 310 9 and its environment, including the Antlia dwarf galaxy, at unprecedented velocity resolution and brightness sensitivity. The H I mass of NGC 3109 is measured to be 3.8 +/- 0.5 x 10(8) M-.. A substantial warp in the disk of NGC 3109 is detected in the H I emission image in the form of an extended l ow surface brightness feature. We report a positive detection in H I of the nearby Antlia dwarf galaxy and measure its total neutral gas mass to be 6. 8 +/- 1.4 x 10(5) M-.. We show the warp in NGC 3109 to lie at exactly the s ame radial velocity as the gas in the Antlia dwarf galaxy and speculate tha t Antlia disturbed the disk of NGC 3109 during a mild encounter similar to1 Gyr in the past. H I data for a further eight galaxies detected in the bac kground are presented.