Was the Progenitor of the Sagittarius Stream a Disc Galaxy?
  We use N-body simulations to explore the possibility that the Sagittarius
(Sgr) dwarf galaxy was originally a late-type, rotating disc galaxy, rather
than a non-rotating, pressure-supported dwarf spheroidal galaxy, as previously
thought. We find that bifurcations in the leading tail of the Sgr stream,
similar to those detected by the SDSS survey, naturally arise in models where
the Sgr disc is misaligned with respect to the orbital plane. Moreover, we show
that the internal rotation of the progenitor may strongly alter the location of
the leading tail projected on the sky, and thus affect the constraints on the
shape of the Milky Way dark matter halo that may be derived from modelling the
Sgr stream. Our models provide a clear, easily-tested prediction: although
tidal mass stripping removes a large fraction of the original angular momentum
in the progenitor dwarf galaxy, the remnant core should still rotate with a
velocity amplitude ~20 km/s that could be readily detected in future,
wide-field kinematic surveys of the Sgr dwarf.
