HI observations of barred Magellanic spirals. II. The frequency and impact of companions

The results of an H I 21 cm line survey of a sample of Magellanic spiral galaxies with apparent optical companions reveal that only four of 13 systems have confirmed H I - detected neighbors. The current interactions are affecting the morphology of the main galaxy in only two cases, NGC 3664 and NGC 3995. The presence of companions near NGC 2537 and UGC 5391 appears to have no effect on the morphology of those galaxies. Overall, there is little difference between the asymmetry of the H I profiles of those galaxies with and without companions, and on average, these Magellanic spirals have H I profiles that are no more asymmetric than a random sample of spirals in the field. We conclude that current interactions cannot be responsible for the lopsided morphology of most of the galaxies in this sample and that, whatever its original cause, lopsidedness must be a long-lived characteristic of these galaxies.