Detalles de publicación
PP 020114
Exploring the stellar age distribution of the Milky Way Bulge using APOGEE
Several institutions from North and South America and Europe (including IAC and ULL)
We present stellar age distributions of the Milky Way (MW) bulge region using ages for ~6,000 high-luminosity (log(g) < 2.0), metal-rich ([Fe/H] > -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Ages are derived using The Cannon label-transfer method, trained on a sample of nearby luminous giants with precise parallaxes for which we obtain ages using a Bayesian isochrone-matching technique. We find that the metal-rich bulge is predominantly composed of old stars (>8 Gyr). We find evidence that the planar region of the bulge (|Z_GC| < 0.25 kpc) enriched in metallicity, Z, at a faster rate (dZ/dt ~ 0.0034 Gyr^-1) than regions farther from the plane (dZ/dt ~ 0.0013 Gyr^-1 at |Z_GC| > 1.00 kpc). We identify a non-negligible fraction of younger stars (age ~2-5 Gyr) at metallicities of +0.2 < [Fe/H] < +0.4. These stars are preferentially found in the plane (|Z_GC| < 0.25 kpc) and between R_cy ~ 2-3 kpc, with kinematics that are more consistent with rotation than are the kinematics of older stars at the same metallicities. We do not measure a significant age difference between stars found in and outside of the bar. These findings show that the bulge experienced an initial starburst that was more intense close to the plane than far from the plane. Then, star formation continued at super-solar metallicities in a thin disk at 2 kpc < R_cy < 3 kpc until ~2 Gyr ago.

