HI in Arp72 and similarities with M51-type systems
  We present neutral hydrogen (H{\sc i}) observations with the Giant Metrewave
Radio Telescope ({\it GMRT}) of the interacting galaxies NGC5996 and NGC5994,
which make up the Arp72 system. Arp72 is an M51-type system and shows a complex
distribution of H{\sc i} tails and a bridge due to tidal interactions. H{\sc i}
column densities ranging from 0.8$-1.8\times10^{20}$ atoms cm$^{-2}$ in the
eastern tidal tail to 1.7$-2\times10^{21}$ atoms cm$^{-2}$ in the bridge
connecting the two galaxies, are seen to be associated with star-forming
regions. We discuss the morphological and kinematic similarities of Arp72 with
M51, the archetypal example of the M51-type systems, and Arp86, another
M51-type system studied with the {\it GMRT}, and suggest that a multiple
passage model of Salo & Laurikainen may be preferred over the classical single
passage model of Toomre & Toomre, to reproduce the H{\sc i} features in Arp72
as well as in other M-51 systems depicting similar optical and H{\sc i}
features.
