The stellar population of the inner 200 parsecs

Abstract

The central 200 pc of the Galaxy is obscured by 5-30 visual magnitudes of extinction and therefore may be studied only in the infrared. The central parsec consists of a mostly red star cluster (IRS 16) and a cluster of ≈ 10 HeI Wolf-Rayet or Of-like stars; this cluster is the best evidence for star formation in this region. The central 5 pc has an extended giant branch (to Mbol/=−6) and long period variables. These stars are not extraordinarily bright; in the central 200 pc luminous asymptotic giant branch (AGB) stars (Mbol < −5) concentrate toward the nucleus in a distribution more flattened than the general light. Candidates for relatively young objects include a rapidly rotating population of high outflow velocity OH/IR stars. The AGB luminosity function in the central 200 pc resembles that recently found in M32 and M31 bulge fields. Depending on how one interprets the extended giant branch, the population may be intermediate age with some ongoing star formation, or mostly old and metal rich, with star formation confined to the nucleus.