FIGURE ROTATION AND THE MASS OF THE GALACTIC BULGE

摘要

The mass of the Galactic bulge, M_B, is estimated from the tensor virial theorem. By including the effects of a barred stellar distribution and figure rotation (81 km s~(-1) kpc~(-1)) and by assuming that the bar is oriented at θ = 20° to our line of sight, M_B is found to be as high as 2.8 x 10~(10) solar mass. This estimate is in good agreement with the total mass inferred from the observed optical depth to microlensing for stars toward the inner Galaxy. For larger angles, θ ～ 40°, or smaller pattern speeds (20 km s~(-1) kpc~(-1)), M_B is found to be ～1.7-1.9 x 10~(10) solar mass, similar to previous estimates for a barred bulge (2 x 10~(10) solar mass) and axisymmetric bulge (1.8 x 10~(10) solar mass).