Milky Way demographics with the VVV Survey III. Evidence for a Great
  Dark Lane in the 157 Million Star Bulge Color-Magnitude Diagram
  The new generation of IR surveys are revealing and quantifying Galactic
features, providing an improved 3-D interpretation of our own Galaxy. We
present an analysis of the global distribution of dust clouds in the bulge
using the near-IR photometry of 157 million stars from the VVV Survey. We
investigate the color magnitude diagram of the Milky Way bulge which shows a
red giant clump of core He burning stars that is split in two color components,
with a mean color difference of (Z-Ks)=0.55 magnitudes equivalent to A_V=2.0
magnitudes. We conclude that there is an optically thick dust lane at
intermediate latitudes above and below the plane, that runs across several
square degrees from l=-10 deg to l=+10 deg. We call this feature the "Great
Dark Lane". Although its exact distance is uncertain, it is located in front of
the bulge. The evidence for a large-scale great dark lane within the Galactic
bulge is important in order to constrain models of the barred Milky Way bulge
and to compare our galaxy with external barred galaxies, where these kinds of
features are prominent. We discuss two other potential implications of the
presence of the Great Dark Lane for microlensing and bulge stellar populations
studies.
