Non-Parametric Density Reconstruction of the Galactic Bulge Area using
  Red Clump Stars in the VVV Survey
  Studies of the red clump giant population in the inner Milky Way suggest the
Galactic bulge/bar has a boxy/peanut/X-shaped structure as predicted by its
formation via a disc buckling instability. We used a non-parametric method of
estimating the Galactic bulge morphology that is based on maximum entropy
regularisation. This enabled us to extract the three-dimensional distribution
of the red giant stars in the bulge from deep photometric catalogues of the
VISTA Variables in the Via Lactea (VVV) survey. Our high-resolution
reconstruction confirms the well-known boxy/peanut/X-shaped structure of the
bulge. We also find spiral arm structures that extend to around three kpc in
front of and behind the bulge and are on different sides of the bulge major
axis. We show that the detection of these structures is robust to the
uncertainties in the luminosity function.
