Exploring the stellar age distribution of the Milky Way Bulge using APOGEE

Abstract

We present stellar age distributions of the Milky Way (MW) bulge region using ages for $\sim$6,000 high-luminosity ($\log (g)<2.0$), metal-rich ($[Fe/H]\ge -0.5$) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Ages are derived using {\it The Cannon} label-transfer method, trained on a sample of nearby luminous giants with precise parallaxes for which we obtain ages using a Bayesian isochrone-matching technique. We find that the metal-rich bulge is predominantly composed of old stars ($>$8 Gyr). We find evidence that the planar region of the bulge ($|Z_{\mathrm{GC}}|\le 0.25$ kpc) enriched in metallicity, $Z$, at a faster rate ($dZ/dt\sim$ 0.0034 $\mathrm{Gy}{\mathrm{r}}^{-1}$) than regions farther from the plane ($dZ/dt\sim$ 0.0013 $\mathrm{Gy}{\mathrm{r}}^{-1}$ at $|Z_{\mathrm{GC}}|>1.00$ kpc). We identify a non-negligible fraction of younger stars (age $\sim$ 2--5 Gyr) at metallicities of $+0.2<[Fe/H]<+0.4$. These stars are preferentially found in the plane ($|Z_{\mathrm{GC}}|\le 0.25$ kpc) and between $R_{\mathrm{cy}}\approx 2-3$ 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 $\lesssim R_{\mathrm{cy}}\lesssim$ 3 kpc until $\sim$2 Gyr ago.

21 pages, 15 figures, accepted for publication in ApJ

References in corpus (29)

• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• The Structure of the Milky Way's Bar Outside the Bulge
• The APOKASC Catalog: An Asteroseismic and Spectroscopic Joint Survey of Targets in the Kepler Fields
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• Target Selection for the SDSS-IV APOGEE-2 Survey
• The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy
• Stellar Population gradients in galaxy discs from the CALIFA survey
• The GIRAFFE Inner Bulge Survey (GIBS) III. Metallicity distributions and kinematics of 26 Galactic bulge fields
• The Gaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge
• Light, Alpha, and Fe-Peak Element Abundances in the Galactic Bulge
• Chemical Evolution of the Galactic Bulge as Derived from High-Resolution Infrared Spectroscopy of K and M Red Giants
• Galaxy Zoo: Secular evolution of barred galaxies from structural decomposition of multi-band images
• A radial age gradient in the geometrically thick disk of the Milky Way
• Atypical Mg-poor Milky Way field stars with globular cluster second-generation like chemical patterns
• Constraining Metallicity-dependent Mixing and Extra Mixing using [C/N] in Alpha-Rich Field Giants
• Metallicity and $\alpha$-element Abundance Gradients along the Sagittarius Stream as Seen by APOGEE
• Deep Mixing and Metallicity: Carbon Depletion in Globular Cluster Giants
• The Chemical Composition of the Galactic Bulge and Implications for its Evolution
• The Bulge Metallicity Distribution from the APOGEE Survey
• Identifying Sagittarius Stream Stars By Their APOGEE Chemical Abundance Signatures
• Mapping the stellar age of the Milky Way bulge with the VVV. I. The method
• SDSS-IV MaNGA: Stellar Population Gradients Within Barred Galaxies
• Kinematics in the Galactic Bulge with APOGEE: II. High-Order Kinematical Moments and Comparison to Extragalactic Bar Diagnostics
• APOGEE [C/N] Abundances Across the Galaxy: Migration and Infall from Red Giant Ages
• What the Milky Way bulge reveals about the initial metallicity gradients in the disc
• The age distribution of stars in the Milky Way bulge

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