H I observations of strongly interacting galaxies

H I observations of small systems of galaxies in some cases reveal the presence of anomalous, sloping velocity shoulders on the integrated H I line profiles. These are interpreted as evidence for ongoing tidal interactions, most probably associated with galaxies in slow hyperbolic encounters in which extensive transfers of orbital to internal energy can produce extreme noncircular motions. The kinematics of such systems therefore provide a means to identify actively interacting galaxies and a method to probe the energetics of collisions between nonbinary galaxies