Does the Sagittarius Stream constrain the Milky Way halo to be triaxial?
  Recent analyses of the stellar stream of the Sagittarius dwarf galaxy have
claimed that the kinematics and three-dimensional location of the M-giant stars
in this structure constrain the dark matter halo of our Galaxy to possess a
triaxial shape that is extremely flattened, being essentially an oblate
ellipsoid oriented perpendicular to the Galactic disk. Using a new
stream-fitting algorithm, based on a Markov Chain Monte Carlo procedure, we
investigate whether this claim remains valid if we allow the density profile of
the Milky Way halo greater freedom. We find stream solutions that fit the
leading and trailing arms of this structure even in a spherical halo, although
this would need a rising Galactic rotation curve at large Galactocentric
radius. However, the required rotation curve is not ruled out by current
constraints. It appears therefore that for the Milky Way, halo triaxiality,
despite its strong theoretical motivation, is not required to explain the
Sagittarius stream. This degeneracy between triaxiality and the halo density
profile suggests that in future endeavors to model this structure, it will be
advantageous to relax the strict analytic density profiles that have been used
to date.
