  We present models of interacting galaxies in order to study the development
of spatial offsets between the gaseous and stellar components in tidal tails.
Observationally, such offsets are observed to exist over large scales (e.g.,
NGC 3690; Hibbard et al. 2000), suggesting an interaction between the tidal gas
and some (unseen) hot ISM. Instead, our models show these offsets are a natural
consequence of the radially extended HI spatial distribution in disk galaxies,
coupled with internal dissipation in the gaseous component driven by the
interaction. This mechanism is most effective in systems involved in very
prograde interactions, and explains the observed gas/star offsets in
interacting galaxies without invoking interactions with a hot ISM, starburst
ionization, or dust obscuration within the tails.

Astrophysics