A LARGE ASYMMETRY IN THE GALACTIC DISTRIBUTION OF FAINT HALO/THICK DISK STARS

摘要

We report a large and significant asymmetry in the number of stars in the first quadrant (l = 20°-45°) of the galaxy compared to complementary longitudes on the other side (fourth quadrant) of the center-anticenter line. This excess in the star counts may be evidence for a triaxial distribution for the thick disk or inner halo of the Galaxy. The stars were chosen to be bluer than B - V ≈ 0.6 mag and are most likely subdwarfs. Assuming these stars are subdwarfs, they are on average approximately 3 kpc away, in the direction and at the same distance as the stellar bar proposed by Weinberg but 1.7 kpc above it. Possible explanations for this excess include an elliptical thick disk, disk heating from an interaction with the Sagittarius dwarf, or heating of the disk by the bar.