Observational Evidence for a Bar in the Milky Way

Abstract

Evidence from a variety of sources points towards the existence of a bar in the central few kpc of the Galaxy. The measurements roughly agree on the direction of the bar major axis, but other parameters (axis ratio, size, pattern speed) are still poorly determined. Current dynamical models are limited by the quality of hydro simulations, the degeneracy of stellar orbit models, stellar-kinematic data and the significant lopsidedness of the central kpc. Microlensing promises new constraints on the mass distribution in the bulge/bar region.