We examine the effect of different dark matter halo potentials on the morphology and kinematics of tidals tails in a merger model of NGC 7252 .
We find that models of merging galaxies with low halo masses of M _ { h } \sim 4 - 8 M _ { disk + bulge } ( M _ { db } ) can fit the observed morphology and kinematics of the NGC 7252 tails while galaxies with high mass halos ( M _ { h } \sim 16 - 32 M _ { db } ) fail in this respect .
In high mass models , the deep potential only allows weakly bound disk material ( stars or gas ) at R \buildrel > \over { \sim } 5 disk scale lengths to be ejected in tidal tails which tend to fall back onto the parent galaxies before the final merger .
Galaxies with massive , low density halos are somewhat more successful at ejecting tidal debris during mergers , but still have difficulties recreating the thin , gas-rich tails observed in NGC 7252 .
Our models suggest upper limits for the dark halo masses in the NGC 7252 progenitor galaxies of roughly M _ { h } \buildrel < \over { \sim } 10 M _ { db } .
We note , however , that our calculations have focused on the rather idealized case of the isolated merging of galaxies with distinct dark matter halos ; calculations which employ more realistic ( “ cosmological ” ) initial conditions are needed to fully explore the use of tidal tails in constraining dark matter in galaxies .