  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 Mh = 4-8
M{disk+bulge} (Mdb) can fit the observed morphology and kinematics of the NGC
7252 tails while galaxies with high mass halos (Mh = 16-32 Mdb) fail in this
respect. In high mass models, the deep potential only allows weakly bound disk
material (stars or gas) at R > 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 Mh <=
10 Mdb. 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.
