The GALAH Survey: Temporal Chemical Enrichment of the Galactic Disk

Abstract

We present isochrone ages and initial bulk metallicities ($[Fe/H{]}_{\mathrm{bulk}}$, by accounting for diffusion) of 163,722 stars from the GALAH Data Release 2, mainly composed of main sequence turn-off stars and subgiants ($7000K>{\mathrm{T}}_{\mathrm{eff}}>4000K$ and $\mathrm{logg}>3$ dex). The local age-metallicity relationship (AMR) is nearly flat but with significant scatter at all ages; the scatter is even higher when considering the observed surface abundances. After correcting for selection effects, the AMR appear to have intrinsic structures indicative of two star formation events, which we speculate are connected to the thin and thick disks in the solar neighborhood. We also present abundance ratio trends for 16 elements as a function of age, across different $[Fe/H{]}_{\mathrm{bulk}}$ bins. In general, we find the trends in terms of [X/Fe] vs age from our far larger sample to be compatible with studies based on small ($\sim$ 100 stars) samples of solar twins but we now extend it to both sub- and super-solar metallicities. The $\alpha$-elements show differing behaviour: the hydrostatic $\alpha$-elements O and Mg show a steady decline with time for all metallicities while the explosive $\alpha$-elements Si, Ca and Ti are nearly constant during the thin disk epoch (ages $⪅$ 12 Gyr). The s-process elements Y and Ba show increasing [X/Fe] with time while the r-process element Eu have the opposite trend, thus favouring a primary production from sources with a short time-delay such as core-collapse supernovae over long-delay events such as neutron star mergers.

References in corpus (26)

• The Transiting Exoplanet Survey Satellite
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dartmouth Stellar Evolution Database
• The K2 Mission: Characterization and Early results
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The GALAH Survey: Scientific Motivation
• Nucleosynthetic signatures of the first stars
• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• NLTE abundances of Mn in a sample of metal-poor stars
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• The age-metallicity structure of the Milky Way disk
• A precise asteroseismic age and radius for the evolved Sun-like star KIC 11026764
• Abundance to age ratios in the HARPS-GTO sample with Gaia DR2: Chemical clocks for a range of [Fe/H]
• The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone
• The temporal evolution of neutron-capture elements in the Galactic discs
• A radial age gradient in the geometrically thick disk of the Milky Way
• The AMBRE project: The thick thin disk and thin thick disk of the Milky Way
• The chemical compositions of solar twins in the open cluster M67
• The GALAH survey: The data reduction pipeline
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• A Unified tool to estimate Distances, Ages and Masses (UniDAM) from spectrophotometric data
• The AMBRE Project: Parameterisation of FGK-type stars from the ESO:HARPS archived spectra
• Yule-Simpson's paradox in Galactic Archaeology
• Chromospherically Active Stars in the RAVE Survey. II. Young dwarfs in the Solar neighborhood

Cited by in corpus (21)

• The GALAH survey: tracing the Galactic disk with Open Clusters
• Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories
• Stellar migrations and metal flows -- Chemical evolution of the thin disc of a simulated Milky Way analogous galaxy
• A Tale of Two Disks: Mapping the Milky Way with the Final Data Release of APOGEE
• VINTERGATAN III: how to reset the metallicity of the Milky Way
• A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper-Centaurus Lupus
• Unveiling the time evolution of chemical abundances across the Milky Way disk with APOGEE
• The K2 Galactic Archaeology Program Data Release 3: Age-abundance patterns in C1-C8 and C10-C18
• Evidence for Metallicity-Dependant Spin Evolution in the Kepler field
• Detailed chemical compositions of planet hosting stars: I. Exploration of possible planet signatures
• The GALAH Survey: Chemical Clocks
• The non-monotonic, strong metallicity dependence of the wide-binary fraction
• Dissecting the Gaia HR diagram within 200 pc
• Combined APOGEE-GALAH stellar catalogues using the Cannon
• Star Formation Timescales of the Halo Populations from Asteroseismology and Chemical Abundances
• Testing abundance-age relations beyond solar analogues with Kepler LEGACY stars
• The [Y/Mg] chemical clock in the Galactic Disk: The influence of metallicity and Galactic population in the solar neighbourhood
• r-Process enrichment in the Galactic halo characterized by nucleosynthesis variation in the ejecta of coalescing neutron star binaries
• The GALAH Survey: Dependence of elemental abundances on age and metallicity for stars in the Galactic disc
• The bi-modal ${}^7$Li distribution of the Milky Way's thin-disk dwarf stars: The role of Galactic-scale events and stellar evolution
• The odd bunch: chrono-chemo-dynamics of sixteen unusual stars from Kepler