Carbon, nitrogen and $\alpha$-element abundances determine the formation sequence of the Galactic thick and thin disks

Abstract

Using the DR12 public release of APOGEE data, we show that thin and thick disk separate very well in the space defined by [$\alpha$/Fe], [Fe/H] and [C/N]. Thick disk giants have both higher [C/N] and higher [$\alpha$/Fe] than do thin disk stars with similar [Fe/H]. We deduce that the thick disk is composed of lower mass stars than the thin disk. Considering the fact that at a given metallicity there is a one-to-one relation between stellar mass and age, we are then able to infer the chronology of disk formation. Both the thick and the thin disks - defined by [$\alpha$/Fe] -- converge in their dependance on [C/N] and [C+N/Fe] at [Fe/H]$\approx$-0.7. We conclude that 1) the majority of thick disk stars formed earlier than did the thin disk stars 2) the formation histories of the thin and thick disks diverged early on, even when the [Fe/H] abundances are similar 3) that the star formation rate in the thin disk has been lower than in the thick disk, at all metallicities. Although these general conclusions remain robust, we also show that current stellar evolution models cannot reproduce the observed C/N ratios for thick disk stars. Unexpectedly, reduced or inhibited canonical extra-mixing is very common in field stars. While subject to abundance calibration zeropoint uncertainties, this implies a strong dependence of non canonical extra-mixing along the red giant branch on the initial composition of the star and in particular on the $\alpha$ elemental abundance.

12 pages, 14 figures, accepted in MNRAS

References in corpus (12)

• The GALAH Survey: Scientific Motivation
• alpha-, r-, and s-process element trends in the Galactic thin and thick disks
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements
• Thermohaline mixing: A physical mechanism governing the photospheric composition of low-mass giants
• The Gaia-ESO Survey: the Galactic Thick to Thin Disc transition
• Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars
• Carbon and oxygen abundances in stellar populations
• The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
• Oxygen abundances in G- and F-type stars from HARPS
• The Rich Are Different: Evidence from the RAVE Survey for Stellar Radial Migration
• Deep Mixing and Metallicity: Carbon Depletion in Globular Cluster Giants
• Inhibition of thermohaline mixing by a magnetic field in Ap star descendants: Implications for the Galactic evolution of 3He

Cited by in corpus (117)

• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• The Thirteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey MApping Nearby Galaxies at Apache Point Observatory
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• The origin of accreted stellar halo populations in the Milky Way using APOGEE, $\text{Gaia}$, and the EAGLE simulations
• Red giant masses and ages derived from carbon and nitrogen abundances
• The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location
• Accuracy and precision of industrial stellar abundances
• Simultaneous calibration of spectro-photometric distances and the Gaia DR2 parallax zero-point offset with deep learning
• Measuring Radial Orbit Migration in the Milky Way Disk
• APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
• Ages and kinematics of chemically selected, accreted Milky Way halo stars
• Overview of the DESI Milky Way Survey
• Isochrone ages for ~3 million stars with the second Gaia data release
• Fundamental parameters and infrared excesses of Tycho-Gaia stars
• The GALAH survey: An abundance, age, and kinematic inventory of the solar neighbourhood made with TGAS
• The Milky Way bar and bulge revealed by APOGEE DR16 and Gaia EDR3
• The AMBRE Project: chemical evolution models for the Milky Way thick and thin discs
• An accurate and self-consistent chemical abundance catalogue for the APOGEE/Kepler sample
• The temporal evolution of neutron-capture elements in the Galactic discs
• PLATO as it is: a legacy mission for Galactic archaeology
• The origin of diverse $\alpha$-element abundances in galaxy discs
• Binary stars in the Galactic thick disc
• The AMBRE project: The thick thin disk and thin thick disk of the Milky Way
• Cannibals in the thick disk: the young $\alpha -$rich stars as evolved blue stragglers
• The Hyades open cluster is chemically inhomogeneous
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Chemical Abundances of Main-Sequence, Turnoff, Subgiant and red giant Stars from APOGEE spectra II: Atomic Diffusion in M67 Stars
• The Gaia-ESO survey: the non-universality of the age-chemical-clocks-metallicity relations in the Galactic disc
• In the Galactic disk, stellar [Fe/H] and age predict orbits and precise [X/Fe]
• Age-resolved chemistry of red giants in the solar neighbourhood
• Spatial variations in the Milky Way disc metallicity-age relation
• Post first dredge-up [C/N] ratio as age indicator. Theoretical calibration
• On the metallicity dependance of the [Y/Mg] - age relation for solar type stars
• Spectroscopic age estimates for APOGEE red-giant stars: Precise spatial and kinematic trends with age in the Galactic disc
• A large and pristine sample of standard candles across the Milky Way: ~100,000 red clump stars with 3% contamination
• Gaia Data Release 3: Chemical cartography of the Milky Way
• The Gaia-ESO survey: impact of extra-mixing on C- and N-abundances of giant stars
• The Gaia-ESO survey: Calibrating a relationship between Age and the [C/N] abundance ratio with open clusters
• Population synthesis to constrain Galactic and Stellar Physics- I- Determining age and mass of thin-disc red-giant stars
• MADE: A spectroscopic Mass, Age, and Distance Estimator for red giant stars with Bayesian machine learning
• Mass and Age of Red Giant Branch Stars Observed with LAMOST and \emph{Kepler}
• Prospects for Galactic and stellar astrophysics with asteroseismology of giant stars in the $TESS$ Continuous Viewing Zones and beyond
• Exploring the stellar age distribution of the Milky Way Bulge using APOGEE
• Chemical Cartography with APOGEE: Mapping Disk Populations with a Two-Process Model and Residual Abundances
• Impacts of a Flaring Star-forming Disc and Stellar Radial Mixing on the Vertical Metallicity Gradient
• Benchmark ages for the Gaia benchmark stars
• Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree
• Chemical separation of disc components using RAVE
• Light Elements in the Universe
• Nitrogen depletion in field red giants: mixing during the He flash?
• The stellar velocity distribution function in the Milky Way galaxy
• Strong chemical tagging with APOGEE: 21 candidate star clusters that have dissolved across the Milky Way disc
• The GALAH Survey: Chemical Clocks
• A variational encoder-decoder approach to precise spectroscopic age estimation for large Galactic surveys
• Most "young" $\alpha$-rich stars have high masses but are actually old
• Blind chemical tagging with DBSCAN: prospects for spectroscopic surveys
• APOGEE [C/N] Abundances Across the Galaxy: Migration and Infall from Red Giant Ages
• Cannibals in the thick disk II -- Radial-velocity monitoring of the young alpha-rich stars
• Photospheric diagnostics of core helium burning in giant stars
• Chemical Abundances in a Sample of Red Giants in the Open Cluster NGC 2420 from APOGEE
• Magnetic-buoyancy-induced mixing in AGB Stars: a theoretical explanation of the non-universal [Y/Mg]-age relation
• Milky Way's Thick and Thin disk: Is there distinct thick disk?
• Deciphering the evolution of the Milky Way discs: Gaia APOGEE Kepler giant stars and the Besançon Galaxy Model
• The Gaia-ESO Survey: the N/O abundance ratio in the Milky Way
• The structural evolution of galaxies with both thin and thick discs
• APOGEE chemical tagging constraint on the maximum star cluster mass in the $\alpha$-enhanced Galactic disk
• Timing the Evolution of the Galactic Disk with NGC 6791: An Open Cluster with Peculiar High-$\alpha$ Chemistry as seen by APOGEE
• Stellar Population Astrophysics (SPA) with TNG. The old open clusters Collinder 350, Gulliver 51, NGC 7044, and Ruprecht 171
• Observing the products of stellar evolution in the old open cluster M67 with APOGEE
• Migration and kinematics in growing disc galaxies with thin and thick discs
• The Open Cluster Chemical Abundances and Mapping Survey: VII. APOGEE DR17 [C/N]-Age Calibration
• The velocity ellipsoid in the Galactic disc using Gaia DR1
• Accelerated Fitting of Stellar Spectra
• The relationship between age, metallicity, and abundances for disk stars in a simulated Milky Way galaxy
• Is Thermohaline Mixing the Full Story? Evidence for Separate Mixing Events near the Red Giant Branch Bump
• The Gaia-ESO survey: Hydrogen lines in red giants directly trace stellar mass
• Universal properties of the high- and low-α disk: small intrinsic abundance scatter and migrating stars
• The structure of the Milky Way based on unWISE 3.4$\mu$m integrated photometry
• CNO abundances and carbon isotope ratios in evolved stars of the open clusters NGC 2324, NGC 2477, and NGC 3960
• A kinematic calibration of the O-rich Mira variable period-age relation from Gaia
• Disentangled Representation Learning for Astronomical Chemical Tagging
• Precise Masses, Ages of ~1.0 million RGB and RC stars observed by the LAMOST
• Stragglers of the thick disc
• Galactic structure in the outer disk: the field in the line of sight to the intermediate-age open cluster Tombaugh 1
• Cardinal kinematics: I. Rotation fields of the APOGEE Survey
• Star Cluster Ages in the Gaia Era
• Characterizing Observed Extra Mixing Trends in Red Giants using the Reduced Density Ratio from Thermohaline Models
• Li-rich Giants in LAMOST Survey. III. The statistical analysis of Li-rich giants
• From the Inner to Outer Milky Way: A Photometric Sample of 2.6 Million Red Clump Stars
• Chemo-Dynamical Clustering applied to APOGEE data: Re-Discovering Globular Clusters
• Exoplanets Across Galactic Stellar Populations with PLATO: Estimating Exoplanet Yields Around FGK Stars for the Thin Disk, Thick Disk and Stellar Halo
• Metallicity Gradient of the Thick Disc Progenitor at High Redshift
• Time evolution of Ce as traced by APOGEE using giant stars observed with the Kepler, TESS and K2 missions
• The vertical metallicity gradients of mono-age stellar populations in the Milky Way with the RAVE and Gaia data
• A Combined Chandra and LAMOST Study of Stellar Activity
• Excitation and charge transfer in low-energy hydrogen atom collisions with neutral carbon and nitrogen
• Modelling chemical clocks -- Theoretical evidences of the space and time evolution of [s/alpha] in the Galactic disc with Gaia-ESO survey
• Chemical composition of giant stars in the open cluster IC 4756
• Homogeneous Stellar Atmospheric Parameters and 22 Elemental Abundances for FGK Stars Derived From LAMOST Low-resolution Spectra with DD-Payne
• Evidence of Deep Mixing in IRS 7, a Cool Massive Supergiant Member of the Galactic Nuclear Star Cluster
• The chemical enrichment of the Milky Way disk evaluated using conditional abundances
• Unveiling the chemical fingerprint of phosphorus-rich stars I. In the infrared region of APOGEE-2
• Extended MCDHF calculations of energy levels and transition data for N I
• Populating The Milky Way: Characterising Planet Demographics by Combining Galaxy Formation Simulations and Planet Population Synthesis Models
• Chemical abundances and ages of the bulge stars in APOGEE high-velocity peaks
• The GALAH Survey: Dependence of elemental abundances on age and metallicity for stars in the Galactic disc
• Element abundance analysis of the metal-rich stellar halo and high-velocitythick disk in the galaxy
• StarFlow: Leveraging Normalizing Flows for Stellar Age Estimation in SDSS-V DR19
• A catalogue of asteroseismically calibrated ages for APOGEE DR17. The predictions of a CatBoost machine learning model based on the [Mg/Ce] chemical clock and other stellar parameters
• New stellar age estimates using SPInS based on Gaia DR3 photometry and LAMOST DR8 abundances
• Weighing stars from birth to death: mass determination methods across the HRD
• A baseline on the relation between chemical patterns and birth stellar cluster
• Vertical kinematics of the thick disc at 4.5 < R < 9.5 kpc
• Calibration of the [C/N] and [Y/Mg] chemical clocks with asteroseismic ages from the TESS space mission
• Two sequences in the age-metallicity relation as seen from [C/N] abundances in APOGEE