The Age of the Galactic Bulge

Abstract

The dominant stellar population of the central bulge of the Milky Way is old, with roughly solar metallicity. The age is very similar to that of the old metal rich bulge globular clusters and to 47 Tucanae, which has an age of 13 Gyr. Stellar composition measurements from Keck/HIRES confirm that the bulge stars are enhanced in Mg and Ti. New HST/NICMOS data are consistent with an old stellar population dominating the central 100 pc of the Milky Way. New infrared photometry has been reported for the bulge of M31. Although bright asymptotic asymptotic giant branch stars are observed in the infrared, the data are most consistent with an old stellar population.