Star Formation Timescales of the Halo Populations from Asteroseismology and Chemical Abundances

Abstract

We combine asteroseismology, optical high-resolution spectroscopy, and kinematic analysis for 26 halo red giant branch stars in the \textit{Kepler} field in the range of $-2.5<[\mathrm{Fe}/\mathrm{H}]<-0.6$. After applying theoretically motivated corrections to the seismic scaling relations, we obtain an average mass of $0.97\pm 0.03{\mathrm{M}}_{\odot }$ for our sample of halo stars. Although this maps into an age of $\sim 7\mathrm{Gyr}$, significantly younger than independent age estimates of the Milky Way stellar halo, we considerer this apparently young age is due to the overestimation of stellar mass in the scaling relations. There is no significant mass dispersion among lower red giant branch stars ($\log g>2$), which constrains a relative age dispersion to $<18\%$, corresponding to $<2\mathrm{Gyr}$. The precise chemical abundances allow us to separate the stars with [{Fe}/{H}]$>-1.7$ into two [{Mg}/{Fe}] groups. While [$\alpha$/{Fe}] and [{Eu}/{Mg}] ratios are different between the two subsamples, [$s$/Eu], where $s$ stands for Ba, La, Ce, and Nd, does not show a significant difference. These abundance ratios suggest that the chemical evolution of the low-Mg population is contributed by type~Ia supernovae, but not by low-to-intermediate mass asymptotic giant branch stars, providing a constraint on its star formation timescale as $100\mathrm{Myr}<\tau <300\mathrm{Myr}$. We also do not detect any significant mass difference between the two [{Mg}/{Fe}] groups, thus suggesting that their formation epochs are not separated by more than 1.5 Gyr.

arXiv comment44 pages. accepted version

References in corpus (170)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• Modules for Experiments in Stellar Astrophysics (MESA)
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Gaia Data Release 2: The astrometric solution
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Local Kinematics and the Local Standard of Rest
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The K2 Mission: Characterization and Early results
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• The Milky Way Tomography with SDSS: I. Stellar Number Density Distribution
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Kepler Mission Design, Realized Photometric Performance, and Early Science
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The New Galaxy: Signatures of its Formation
• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• The mass distribution and gravitational potential of the Milky Way
• Tracing Galaxy Formation with Stellar Halos I: Methods
• Co-formation of the Galactic disc and the stellar halo
• Observational clues to the progenitors of Type-Ia supernovae
• The Radial Velocity Experiment (RAVE): first data release
• The CoRoT satellite in flight : description and performance
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• Na-O Anticorrelation and HB. VII. The chemical composition of first and second-generation stars in 15 globular clusters from GIRAFFE spectra
• Gaia Data Release 2: Photometric content and validation
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• A large stellar evolution database for population synthesis studies. II. Stellar models and isochrones for an alpha-enhanced metal distribution
• Debris streams in the solar neighbourhood as relicts from the formation of the Milky Way
• The Ages of Stars
• Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics
• Near-Field Cosmology with Metal-Poor Stars
• Asteroseismology of Solar-Type and Red-Giant Stars
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The ACS Survey of Galactic Globular Clusters. VII. Relative Ages
• Abundances and Kinematics of Field Halo and Disk Stars I: Observational Data and Abundance Analysis
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• A Search for Stars of Very Low Metal Abundance. VI. Detailed Abundances of 313 Metal-Poor Stars
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• Building up the Stellar Halo of the Galaxy
• Origin of the system of globular clusters in the Milky Way
• The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars
• Testing Scaling Relations for Solar-Like Oscillations from the Main Sequence to Red Giants using Kepler Data
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• The formation and assembly history of the Milky Way revealed by its globular cluster population
• Spectroscopic Studies of Extremly Metal-Poor Stars with Subaru/HDS:II.The r-process Elements, Including Thorium
• Chemical evolution with rotating massive star yields: I. The solar neighbourhood and the s-process elements
• The APOKASC Catalog: An Asteroseismic and Spectroscopic Joint Survey of Targets in the Kepler Fields
• The Second APOKASC Catalog: The Empirical Approach
• The Biggest Splash
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• The r-Process Enriched Low Metallicity Giant HD 115444
• Synthetic Stellar Photometry - I. General considerations and new transformations for broad-band systems
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• The birth of the Milky Way as uncovered by accurate stellar ages with Gaia
• Red giant masses and ages derived from carbon and nitrogen abundances
• Asteroseismology of red giants from the first four months of Kepler data: Fundamental parameters
• Fundamental Properties of Stars using Asteroseismology from Kepler & CoRoT and Interferometry from the CHARA Array
• Delay Time Distribution Measurement of Type Ia Supernovae by the Subaru/XMM-Newton Deep Survey and Implications for the Progenitor
• Asteroseismic classification of stellar populations among 13000 red giants observed by Kepler
• Abundances of 30 elements in 23 metal-poor stars
• Neutron Star Mergers Might not be the Only Source of r-Process Elements in the Milky Way
• Near-UV Observations of HD221170: New Insights into the Nature of r-Process-Rich Stars
• Asteroseismology of 16000 Kepler Red Giants: Global Oscillation Parameters, Masses, and Radii
• A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
• On detecting the large separation in the autocorrelation of stellar oscillation times series
• The GALAH Survey: Observational Overview and Gaia DR1 companion
• Accreted versus In Situ Milky Way Globular Clusters
• Spectroscopic determination of masses (and implied ages) for red giants
• Non-standard s process in low metallicity massive rotating stars
• Stellar population synthesis based modelling of the Milky Way using asteroseismology of 13000 Kepler red giants
• Spectroscopic Studies of Very Metal-Poor Stars with the Subaru High Dispersion Spectrograph. III. Light Neutron-Capture Elements
• The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample
• Testing the asteroseismic scaling relations for Red Giants with Eclipsing Binaries Observed by Kepler
• Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars
• Young [$\alpha$/Fe]-enhanced stars discovered by CoRoT and APOGEE: What is their origin?
• Age dissection of the Milky Way discs: red giants in the Kepler field
• Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy
• Globular clusters in the outer Galactic halo: new HST/ACS imaging of 6 globular clusters and the Galactic globular cluster age-metallicity relation
• Two distinct halo populations in the solar neighborhood. II. Evidence from stellar abundances of Mn, Cu, Zn, Y, and Ba
• The Chemical Homogeneity of Sun-like Stars in the Solar Neighborhood
• Chemical abundances of the Milky Way thick disk and stellar halo II.: sodium, iron-peak and neutron-capture elements
• Neutron Star Mergers as sites of r-process Nucleosynthesis and Short Gamma-Ray Bursts
• Confirmation of the $Gaia$ DR2 parallax zero-point offset using asteroseismology and spectroscopy in the $Kepler$ field
• Confirming chemical clocks: asteroseismic age dissection of the Milky Way disk(s)
• Observational evidence for a broken Li Spite plateau and mass-dependent Li depletion
• Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA
• Ages and kinematics of chemically selected, accreted Milky Way halo stars
• LAMOST observations in the Kepler field. Database of low-resolution spectra
• The R-Process Alliance: First Release from the Northern Search for r-Process Enhanced Metal-Poor Stars in the Galactic Halo
• Global structure and kinematics of stellar haloes in cosmological hydrodynamic simulations
• Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components
• Abundance to age ratios in the HARPS-GTO sample with Gaia DR2: Chemical clocks for a range of [Fe/H]
• Ionization balance of Ti in the photospheres of the Sun and four late-type stars
• Carbon and oxygen abundances in stellar populations
• Non-LTE oxygen line formation in 3D hydrodynamic model stellar atmospheres
• The GALAH survey: An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS
• Two distinct halo populations in the solar neighborhood. III. Evidence from stellar ages and orbital parameters
• Determining stellar parameters of asteroseismic targets: going beyond the use of scaling relations
• VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook dwarf spheroidal galaxy
• Tracing the formation of the Milky Way through ultra metal-poor stars
• Towards stellar effective temperatures and diameters at one per cent accuracy for future surveys
• On the kinematic detection of accreted streams in the Gaia era: a cautionary tale
• Characterisation of red-giant stars in the public Kepler data
• The Solar Twin Planet Search III. The [Y/Mg] clock: estimating stellar ages of solar-type stars
• Testing the Asteroseismic Mass Scale Using Metal-Poor Stars Characterized with APOGEE and Kepler
• The temporal evolution of neutron-capture elements in the Galactic discs
• Origin of the excess of high-energy retrograde stars in the Galactic halo
• Galactic Archaeology with asteroseismology and spectroscopy: Red giants observed by CoRoT and APOGEE
• Accurate and homogeneous abundance patterns in solar-type stars of the solar neighbourhood: a chemo-chronological analysis
• Binary stars in the Galactic thick disc
• Cannibals in the thick disk: the young $\alpha -$rich stars as evolved blue stragglers
• Non standard s-process in massive rotating stars. Yields of $10-150$ $M_{\odot }$ models at $Z=10^{-3}$
• Significantly improving stellar mass and radius estimates: A new reference function for the Δν scaling relation
• High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age
• Age-resolved chemistry of red giants in the solar neighbourhood
• Detection of solar-like oscillations in relics of the Milky Way: asteroseismology of K giants in M4 using data from the NASA K2 mission
• Three Ancient Halo Subgiants: Precise Parallaxes, Compositions, Ages, and Implications for Globular Clusters
• Age dating of an early Milky Way merger via asteroseismology of the naked-eye star $\nu$ Indi
• The Gaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs - Implications for stellar and Galactic chemical evolution
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• Testing the radius scaling relation with $Gaia$ DR2 in the $Kepler$ field
• The age of the Milky Way halo stars from the Sloan Digital Sky Survey
• LAMOST observations in the Kepler field. II. Database of the low-resolution spectra from the five-year regular survey
• Determining Ages of APOGEE Giants with Known Distances
• Heavy elements in Globular Clusters: the role of AGB stars
• Oscillating red giants in eclipsing binary systems: empirical reference value for asteroseismic scaling relation
• Pristine IX: CFHT ESPaDOnS Spectroscopic Analysis of 115 Bright Metal-Poor Candidate Stars
• Spectroscopic Studies of Extremely Metal-Poor Stars with the Subaru High Dispersion Spectrograph. IV. The alpha-Element-Enhanced Metal-Poor Star BS16934-002
• Constraining cosmic scatter in the Galactic halo through a differential analysis of metal-poor stars
• GRACES observations of young [alpha/Fe]-rich stars
• Ages and Masses of 0.64 million Red Giant Branch stars from the LAMOST Galactic Spectroscopic Survey
• The Age of the Galactic Stellar Halo from Gaia White Dwarfs
• Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563 and HD 103095 from CHARA interferometry
• Mass and Age of Red Giant Branch Stars Observed with LAMOST and \emph{Kepler}
• Evidence for the Third Stellar Population in the Milky Way's Disk
• Probing the deep end of the Milky Way with \emph{Kepler}: Asteroseismic analysis of 854 faint Red Giants misclassified as Cool Dwarfs
• Enormous Li-enhancement preceding red giant phases in low-mass stars in the Milky Way halo
• Testing Asteroseismic Scaling Relations using Eclipsing Binaries in Star Clusters and the Field
• Evidence for $\gtrsim 4$ Gyr timescales of neutron star mergers from Galactic archaeology
• Statistical equilibrium of silicon in the atmospheres of metal-poor stars
• The age structure of the Milky Way's halo
• LAMOST observations in the Kepler field. Analysis of the stellar parameters measured with the LASP based on the low-resolution spectra
• Galactic evolution of Copper in the light of NLTE computations
• On the Relative Ages of the $\alpha$-Rich and $\alpha$-Poor Stellar Populations in the Galactic Halo
• The image slicer for the Subaru Telescope High Dispersion Spectrograph
• Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood
• Photospheric diagnostics of core helium burning in giant stars
• NPOI Measurements of Ten Stellar Oscillators
• Spectroscopic study of red giants in the Kepler field with asteroseismologically established evolutionary status and stellar parameters
• Jurassic: A Chemically Anomalous Structure in the Galactic Halo
• The GALAH Survey: Temporal Chemical Enrichment of the Galactic Disk
• NLTE analysis of copper lines in different stellar populations
• The Hamburg/ESO R-process Enhanced Star survey (HERES) VI. The Galactic Chemical Evolution of Silicon
• Optical high-resolution spectroscopy of 14 young $\alpha$-rich stars
• The spectroscopic indistinguishability of red giant branch and red clump stars
• Sc and neutron-capture abundances in Galactic low- and high-alpha field halo stars
• Fundamental stellar parameters and age-metallicity relation of Kepler red giants in comparison with theoretical evolutionary tracks
• Infrared colours and inferred masses of metal-poor giant stars in the Kepler field
• First detection of oscillations in the Halo giant HD 122563: validation of seismic scaling relations and new fundamental parameters
• The Early Merger that Made the Galaxy's Stellar Halo
• Connecting the local stellar halo and its dark matter density to dwarf galaxies via blue stragglers

Cited by in corpus (14)

• $R$-process enhancements of Gaia-Enceladus in GALAH DR3
• GASTRO library I: the simulated chemodynamical properties of several GSE-like stellar halos
• Spectroscopic age estimates for APOGEE red-giant stars: Precise spatial and kinematic trends with age in the Galactic disc
• High-precision chemical abundances of Galactic building blocks. The distinct chemical abundance sequence of Sequoia
• A Comparative Analysis of the Chemical Compositions of Gaia-Enceladus/Sausage and Milky Way Satellites using APOGEE
• The detailed chemical abundance patterns of accreted halo stars from the optical to infrared
• The chemical composition of globular clusters in the Local Group
• Age-Dating Red Giant Stars Associated with Galactic Disk and Halo Substructures
• Cannibals in the thick disk II -- Radial-velocity monitoring of the young alpha-rich stars
• Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental abundances
• A Unified Exploration of the Chronology of the Galaxy
• Pushing the boundaries of asteroseismic individual frequency modelling: unveiling two evolved very-low metallicity red giants
• Uncertainties in asteroseismic grid-based estimates of the ages of halo stars
• Not all nitrogen-rich field stars originate from globular clusters