J/ApJ/901/109 Ages & [Fe/H] of the MW bulge using APOGEE (Hasselquist+, 2020)
Exploring the stellar age distribution of the Milky Way bulge using APOGEE.
Hasselquist S., Zasowski G., Feuillet D.K., Schultheis M.,
Nataf D.M., Anguiano B., Beaton R.L., Beers T.C., Cohen R.E., Cunha K.,
Fernandez-Trincado J.G., Garcia-Hernandez D.A., Geisler D., Holtzman J.A.,
Johnson J., Lane R.R., Majewski S.R., Moni Bidin C., Nitschelm C.,
Roman-Lopes A., Schiavon R., Smith V.V., Sobeck J.
<Astrophys. J., 901, 109 (2020)>
=2020ApJ...901..109H 2020ApJ...901..109H
ADC_Keywords: Milky Way; Abundances, [Fe/H]; Stars, ages; Spectra, infrared
Keywords: Galactic bulge ; Milky Way Galaxy ; Milky Way evolution ;
Milky Way formation ; Stellar ages ; Galaxy bulges
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 (>8Gyr). We find evidence that the
planar region of the bulge (|ZGC|≤0.25kpc) is enriched in
metallicity, Z, at a faster rate (dZ/dt∼0.0034Gyr-1) than regions
farther from the plane (dZ/dt∼0.0013Gyr-1 at |ZGC|>1.00kpc). We
identify a nonnegligible fraction of younger stars (age ∼2-5Gyr) at
metallicities of +0.2<[Fe/H]<+0.4. These stars are preferentially
found in the plane (|ZGC|≤0.25kpc) and at Rcy∼2-3kpc, 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 2kpc≲Rcy≲3kpc until ∼2Gyr ago.
Description:
Observations were taken as part of the APOGEE (see III/284).
The APOGEE instruments are high-resolution, near-infrared
spectrographs observing from both the Northern Hemisphere at Apache
Point Observatory (APO) using the SDSS 2.5m telescope and the Southern
Hemisphere at Las Campanas Observatory (LCO) using the 2.5m du Pont
telescope. As of 2019 December, the dual APOGEE instruments have
observed some 500000 stars across the Milky Way.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 64 46277 Ages produced in this work
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
J/A+A/349/L69 : Interstellar extinction (Schultheis+, 1999)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
J/A+A/486/177 : Bulge field stars from FLAMES-GIRAFFE sp. (Zoccali+, 2008)
J/AJ/138/1243 : The star formation history of the LMC (Harris+, 2009)
J/ApJ/721/L28 : Red clump stars in Gal. Bulge from OGLE-III (Nataf+, 2010)
J/ApJ/733/L47 : Galaxy bulge types within 11Mpc (Fisher+, 2011)
J/A+A/534/A80 : Bulge clump giant abund. in Baade's window (Hill+, 2011)
J/ApJ/732/108 : Abundances of 92 giants in Plaut's window (Johnson+, 2011)
J/A+A/543/A106 : UBVRI photometry in NGC6791 (Brogaard+, 2012)
J/ApJ/749/175 : Abundances for stars in Plaut's window (Johnson+, 2012)
J/A+A/549/A147 : Abund. of microlensed bulge dwarf stars. V. (Bensby+, 2013)
J/ApJ/765/157 : Abund. of red giants in the Galactic bulge (Johnson+, 2013)
J/A+A/558/A53 : MW global survey of star clusters. II. (Kharchenko+, 2013)
J/A+A/559/A98 : JK photometry in BUL_SC9 and BUL_SC29 (Valenti+, 2013)
J/AJ/148/67 : Abundances of 156 bulge red giants (Johnson+, 2014)
J/ApJS/215/19 : APOKASC catalog of Kepler red giants (Pinsonneault+, 2014)
J/ApJ/808/16 : Cannon: a new approach to determine abundances (Ness+, 2015)
J/MNRAS/455/2216 : Outer bulge O-rich Mira's JHKL photometry (Catchpole+, 2016)
J/ApJ/817/40 : High-resolution NIR sp. of local giants (Feuillet+, 2016)
J/AJ/151/144 : ASPCAP weights for APOGEE chemical elements (Garcia+, 2016)
J/MNRAS/456/3655 : Masses and ages of red giants (Martig+, 2016)
J/ApJ/823/114 : The Cannon: a new approach to determine masses (Ness+, 2016)
J/ApJ/819/2 : APOGEE kinematics. I. Galactic bulge overview (Ness+, 2016)
J/A+A/605/A89 : Abund. of microlensed Bulge dwarf stars. VI. (Bensby+, 2017)
J/MNRAS/465/501 : APOGEE N-rich stars in inner Galaxy (Schiavon+, 2017)
J/A+A/599/A12 : [Fe/H] & kinematics of 26 Gal. bulge fields (Zoccali+, 2017)
J/A+A/618/A93 : Gaia DR2 open clusters in the MW (Cantat-Gaudin+, 2018)
J/AJ/156/126 : Parameters & abund. from BACCHUS analysis (Jonsson+, 2018)
J/MNRAS/473/4731 : Barred galaxies structural decomposition (Kruk+, 2018)
J/ApJS/239/32 : APOKASC-2 cat. of Kepler evolved stars (Pinsonneault+, 2018)
J/AJ/156/18 : APOGEE companions of evolved stars (Price-Whelan+, 2018)
J/A+A/618/A147 : Fraction of bulge metal poor & rich stars (Zoccali+, 2018)
J/ApJ/872/58 : Sagittarius stream stars with APOGEE (Hasselquist+, 2019)
J/ApJ/872/137 : Abund. of red clump & RGB with APOGEE (Shetrone+, 2019)
J/ApJ/889/63 : Properties of Sgr Stars (Hayes+, 2020)
J/A+A/638/A76 : StarHorse data for 5 surveys (Queiroz+, 2020)
J/ApJ/900/4 : Abund. & ages of stars in the Milky Way bulge (Sit+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ID APOGEE identifier (2MHHMMSSss+DDMMSSs or
APHHMMSSss+DDMMSSs)
20- 35 A16 --- Field APOGEE field
37- 42 A6 --- Tel Telescope identifier (1)
44- 48 F5.2 [yr] logAge [7.3/11.8] log age
50- 53 F4.2 [yr] e_logAge [0.19/0.4] Uncertainty in logAge
55- 59 F5.2 [Sun] [Fe/H] [-0.54/0.6] Metallicity
61- 64 F4.2 [Sun] e_[Fe/H] [0.01/0.03] Uncertainty in [Fe/H]
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Note (1): Telescope as follows:
apo25m = Northern Hemisphere at Apache Point Observatory (APO) using
the SDSS 2.5m telescope (34179 occurrences)
lco25m = Southern Hemisphere at Las Campanas Observatory (LCO) using
the 2.5m du Pont telescope (12098 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jan-2022