Recovering the mass profile and orbit anisotropy of mock dwarf galaxies
  with Schwarzschild modelling
  We present a new study concerning the application of the Schwarzschild orbit
superposition method to model spherical galaxies. The method aims to recover
the mass and the orbit anisotropy parameter profiles of the objects using
measurements of positions and line-of-sight velocities usually available for
resolved stellar populations of dwarf galaxies in the Local Group. To test the
reliability of the method, we used different sets of mock data extracted from
four numerical realizations of dark matter haloes. The models shared the same
density profile but differed in anisotropy profiles, covering a wide range of
possibilities, from constant to increasing and decreasing with radius. The
tests were done in two steps, first assuming that the mass profile of the dwarf
is known and employing the method to retrieve the anisotropy only, and then
varying also the mass distribution. We used two kinds of data samples:
unrealistically large ones based on over 270 000 particles from the numerical
realizations and small ones matching the amount of data available for the
Fornax dwarf. For the large data samples we recover both the mass and the
anisotropy profiles with very high accuracy. For the realistically small ones
we also find a reasonably good agreement between the fitted and the input
anisotropies, however the total density profiles can be significantly biased as
a result of their oversensitivity to the available data. Our results therefore
provide convincing evidence in favour of the applicability of the Schwarzschild
method to break the mass-anisotropy degeneracy in dwarf galaxies.
