Figure rotation and the mass of the galactic bulge

The mass of the Galactic bulge, MB, is estimated from the tensor virial theorem. By including the effects of a barred stellar distribution and figure rotation (81 kpc ⁻¹) and by assuming that the bar is oriented at θ $=$ 20°\ to our line of sight, MB is found to be as high as 2.8×10¹⁰ M_. 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 kpc ⁻¹), MB is found to be ~ 1.7 $-$ 1.9×10¹⁰ M_, similar to previous estimates for a barred bulge (2×10¹⁰ M_) and axisymmetric bulge (1.8×10¹⁰ M_).