Gas/Star Offsets in Tidal Tails
  We use numerical simulations to study the development of gas/star offsets in the tidal tails of merging galaxies. These offsets are shown to be 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 explains the observed gas/star offsets in interacting galaxies without invoking interactions with a hot (unseen) gaseous component. 
Chris Mihos (Case Western Reserve University)