The development of gas/star offsets in tidal tails

We present models of interacting galaxies in order to study the development of spatial offsets between the gaseous and stellar components in tidal tai ls. Observationally, such large-scale offsets are observed in several syste ms-most notably NGC 3690-suggesting an interaction between the tidal gas an d some (unseen) hot interstellar medium (ISM). Instead, our models show tha t these offsets are a natural consequence of the radially extended H I spat ial distribution in disk galaxies, coupled with internal dissipation in the gaseous component driven by the interaction. This mechanism is most effect ive in systems involved in very prograde interactions and explains the obse rved gas/star offsets in interacting galaxies without invoking interactions with a hot ISM, starburst ionization, or dust obscuration within the tails .