Discy dwarf disruption and the shape of the Galactic halo
  The shape of the Galactic dark halo can, in principle, be inferred through
modelling of stellar tidal streams in the Milky Way halo. The brightest and the
longest of these, the Sagittarius stream, reaches out to large Galactocentric
distances and hence can deliver the tightest constraints on the Galaxy's
potential. In this contribution, we revisit the idea that the Sagittarius
Stream was formed from a rotating progenitor. We demonstrate that the angle
between the disk's angular momentum and the progenitor's orbital angular
momentum does not remain constant throughout the disruption. Instead, it
undergoes a dramatic evolution caused, in part, by the changes in the
progenitor's moment of inertia tensor. We show that, even in a spherical
potential, the streams produced as a result of a disky dwarf disruption appear
to be "precessing". Yet, this debris plane evolution is illusory as it is
solely caused by the swaying and wobbling of the progenitor's disk. Stream
plane precession is therefore not an unambiguous indicator of asphericity of
the dark halo.
