Weighing the two stellar components of the Galactic Bulge
  Recent spectroscopic surveys of the Galactic bulge have unambiguously shown
that the bulge contains two main components, that are best separated in their
iron content, but also differ in spatial distribution, kinematics, and
abundance ratios. The so-called metal poor (MP) component peaks at [Fe/H]~-0.4,
while the metal rich (MR) one peaks at [Fe/H]$~+0.3. The total metallicity
distribution function is therefore bimodal, with a dip at [Fe/H]~0. The
relative fraction of the two components changes significantly across the bulge
area. We provide, for the first time, the fractional contribution of the MP and
MR stars to the stellar mass budget of the Galactic bulge, and its variation
across the bulge area. We find that MP stars make up 48% of the total stellar
mass of the bulge, within the region |l|<10, |b|<9.5, with the remaining 52%
made up of MR stars. The latter dominate the mass budget at intermediate
latitudes |b|~4, but become marginal in the outer bulge (|b|>8). The MP
component is more axisymmetric than the MR one, and it is at least comparable,
and possibly slightly dominant in the inner few degrees. As a result, the MP
component, which does not follow the main bar, is not marginal in terms of the
total mass budget as previously thought, and this new observational evidence
must be included in bulge models. While the total radial velocity dispersion
has a trend that follows the total stellar mass, when we examine the velocity
dispersion of each component individually, we find that MP stars have higher
velocity dispersion where they make up a smaller fraction of the stellar mass,
and viceversa. This is due to the kinematical and spatial distribution of the
two metallicity component being significantly different, as already discussed
in the literature.
