The stars and gas that comprise the tails will have been pulled from the easily distorted galactic discs (or other extremities) of one or both bodies, rather than the gravitationally bound galactic centers. Two very prominent examples of collisions producing tidal tails are the Mice Galaxies and the Antennae Galaxies.
The debris that makes up the tails will have been torn from the easily warped outer edges (or other protrusions) of one or both celestial bodies, rather than their gravitationally tied centers. Two well-known instances of collisions resulting in tidal tails are the Mice Galaxies and the Antennae Galaxies.