Ages of 70 dwarfs of three populations in the solar neighborhood: considering O and C abundances in stellar models

Abstract

Oxygen and carbon are important elements in stellar populations. Their behavior refers to the formation history of the stellar populations. C and O abundances would also obviously influence stellar opacities and the overall metal abundance $Z$. With observed high-quality spectroscopic properties, we construct stellar models with C and O elements, to give more accurate ages for 70 metal-poor dwarfs, which have been determined to be high-$\alpha$ halo, low-$\alpha$ halo and thick-disk stars. Our results show that high-$\alpha$ halo stars are relatively older than low-$\alpha$ halo stars by around 2.0 Gyr. The thick-disk population has an age range between the two halo populations. The age distribution profiles indicate that high-$\alpha$ halo and low-$\alpha$ halo stars match the in situ accretion simulation by Zolotov et al., and the thick-disk stars might be formed in a relatively quiescent and long-lasting process. We also note that stellar ages are very sensitive to O abundance, since the ages clearly increase with increasing [O/Fe] values. Additionally, we obtain several stars with peculiar ages, including 2 young thick-disk stars and 12 stars older than the universe age.

arXiv comment23 pages, 5 figures, ApJ accepted

References in corpus (42)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Evolutionary tracks and isochrones for low- and intermediate-mass stars: from 0.15 to 7 M_sun, and from Z=0.0004 to 0.03
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• The Dartmouth Stellar Evolution Database
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• Low Temperature Opacities
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• GAIA: Composition, Formation and Evolution of the Galaxy
• Galactic chemical evolution: Carbon through Zinc
• Ages for illustrative field stars using gyrochronology: viability, limitations and errors
• Towards Better Age Estimates for Stellar Populations: The Y^2 Isochrones for Solar Mixture
• Element Diffusion in the Solar Interior
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program.Galactic stellar populations and planets
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) The survey science plan
• The age structure of stellar populations in the solar vicinity. Clues of a two-phase formation history of the Milky Way disk
• The YY Isochrones for alpha-element Enhanced Mixtures
• The Dual Origin of Stellar Halos
• The Y^2 Stellar Evolutionary Tracks
• The Milky Way has no thick disk
• Asteroseismology of red giants from the first four months of Kepler data: Fundamental parameters
• Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
• YREC: The Yale Rotating Stellar Evolution Code
• The stellar population structure of the Galactic disk
• Two distinct halo populations in the solar neighborhood. II. Evidence from stellar abundances of Mn, Cu, Zn, Y, and Ba
• Kinematics and chemical properties of the Galactic stellar populations. The HARPS FGK dwarfs sample
• Determination of stellar radii from asteroseismic Data
• Carbon and oxygen abundances in stellar populations
• Tracing Sagittarius Structure with SDSS and SEGUE Imaging and Spectroscopy
• Two distinct halo populations in the solar neighborhood. III. Evidence from stellar ages and orbital parameters
• The Dual Origin of Stellar Halos II: Chemical Abundances as Tracers of Formation History
• Oxygen abundances in low- and high-alpha field halo stars and the discovery of two field stars born in globular clusters
• Metallicity effects on the chromospheric activity-age relation for late-type dwarfs
• The C+N+O abundances and the splitting of the subgiant branch in the Globular Cluster NGC 1851
• Systematic NLTE study of the -2.6 < [Fe/H] < 0.2 F and G dwarfs in the solar neighbourhood. I. Stellar atmosphere parameters
• Three Ancient Halo Subgiants: Precise Parallaxes, Compositions, Ages, and Implications for Globular Clusters
• On the primordial scenario for abundance variations within globular clusters. The isochrone test
• The age of the Milky Way halo stars from the Sloan Digital Sky Survey
• Solar Models with Revised Abundances and Opacities
• On the Relative Ages of the $\alpha$-Rich and $\alpha$-Poor Stellar Populations in the Galactic Halo
• Two distinct halo populations in the solar neighborhood. IV. Lithium abundances
• Asteroseismic analysis of two alpha-enhanced stars KIC 7976303 and KIC 8694723

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