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Exploring the stellar age distribution of the milky way bulge using APOGEE

Hasselquist, Sten ; Zasowski, Gail ; Feuillet, Diane K. LU orcid ; Schultheis, Mathias ; Nataf, David M. ; Anguiano, Borja ; Beaton, Rachael L. ; Beers, Timothy C. ; Cohen, Roger E. and Cunha, Katia , et al. (2020) In Astrophysical Journal 901(2).
Abstract

We present stellar age distributions of the Milky Way bulge region using ages for ∼6000 high-luminosity (log(g)< 2.0), metal-rich ([Fe/H] ≥ -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment. 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 (ZGC| 0.25 kpc) is 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 | ZGC| > 1.00 kpc). We... (More)

We present stellar age distributions of the Milky Way bulge region using ages for ∼6000 high-luminosity (log(g)< 2.0), metal-rich ([Fe/H] ≥ -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment. 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 (ZGC| 0.25 kpc) is 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 | ZGC| > 1.00 kpc). We identify a nonnegligible 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 (ZGC| ≤ 0.25 kpc) and at 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 inside and outside 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 supersolar metallicities in a thin disk at 2 kpc ≲ R cy ≲ 3 kpc until ∼2 Gyr ago.

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type
Contribution to journal
publication status
published
subject
in
Astrophysical Journal
volume
901
issue
2
article number
109
publisher
American Astronomical Society
external identifiers
  • scopus:85092514776
ISSN
0004-637X
DOI
10.3847/1538-4357/abaeee
language
English
LU publication?
yes
id
2966b77b-c204-4222-9c3e-6b4c38302a03
date added to LUP
2021-01-08 11:52:24
date last changed
2024-04-03 18:50:15
@article{2966b77b-c204-4222-9c3e-6b4c38302a03,
  abstract     = {{<p>We present stellar age distributions of the Milky Way bulge region using ages for ∼6000 high-luminosity (log(g)&lt; 2.0), metal-rich ([Fe/H] ≥ -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment. 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 (&gt;8 Gyr). We find evidence that the planar region of the bulge (ZGC| 0.25 kpc) is 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 | ZGC| &gt; 1.00 kpc). We identify a nonnegligible fraction of younger stars (age ∼2-5 Gyr) at metallicities of +0.2 &lt; [Fe/H] &lt; +0.4. These stars are preferentially found in the plane (ZGC| ≤ 0.25 kpc) and at 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 inside and outside 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 supersolar metallicities in a thin disk at 2 kpc ≲ R cy ≲ 3 kpc until ∼2 Gyr ago. </p>}},
  author       = {{Hasselquist, Sten and Zasowski, Gail and Feuillet, Diane K. and Schultheis, Mathias and Nataf, David M. and Anguiano, Borja and Beaton, Rachael L. and Beers, Timothy C. and Cohen, Roger E. and Cunha, Katia and Fernández-Trincado, José G. and García-Hernández, D. A. and Geisler, Doug and Holtzman, Jon A. and Johnson, Jennifer and Lane, Richard R. and Majewski, Steven R. and Bidin, Christian Moni and Nitschelm, Christian and Roman-Lopes, Alexandre and Schiavon, Ricardo and Smith, Verne V. and Sobeck, Jennifer}},
  issn         = {{0004-637X}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{Exploring the stellar age distribution of the milky way bulge using APOGEE}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/abaeee}},
  doi          = {{10.3847/1538-4357/abaeee}},
  volume       = {{901}},
  year         = {{2020}},
}