Mapping the X-Shaped Milky Way Bulge
  We analyzed the distribution of the RC stars throughout Galactic bulge using
2MASS data. We mapped the position of the red clump in 1 sq.deg. size fields
within the area |l|<=8.5deg and $3.5deg<=|b|<=8.5deg, for a total of 170
sq.deg. The red clump seen single in the central area splits into two
components at high Galactic longitudes in both hemispheres, produced by two
structures at different distances along the same line of sight. The X-shape is
clearly visible in the Z-X plane for longitudes close to $l=0 deg axis. Crude
measurements of the space densities of RC stars in the bright and faint RC
populations are consistent with the adopted RC distances, providing further
supporting evidence that the X-structure is real, and that there is approximate
front-back symmetry in our bulge fields. We conclude that the Milky Way bulge
has an X-shaped structure within $|l|<~2deg, seen almost edge on with respect
to the line of sight. Additional deep NIR photometry extending into the
innermost bulge regions combined with spectroscopic data is needed in order to
discriminate among the different possibilities that can cause the observed
X-shaped structure.
