Seminar
The Milky Way Bulge

Abstract

The structure, kinematics and stellar population of the Galactic bulge is very complex. Only three years ago the bulge was discovered to be X-shaped, a structure believed to originate from the dynamical instabilities of a disk, through the formation and posterior heating of a bar. The study of its kinematics reveals a cylindrical rotation, typical of a bar, suggesting the absence of a spheroidal component. Nevertheless, the bulge stellar population is old, has a radial metallicity gradient, and element ratio indicative of a short formation timescale. All these elements conflict with a simplistic view of the bulge as a heated bar, formed via "secular" evolution of a disk. I will review our knowledge of the bulge properties as traced by the 3D structure, kinematics, and chemical composition of its red clump stars.