The abundances of carbon , oxygen , and iron in late-type stars are important parameters in exoplanetary and stellar physics , as well as key tracers of stellar populations and Galactic chemical evolution .
However , standard spectroscopic abundance analyses can be prone to severe systematic errors , based on the assumption that the stellar atmosphere is one-dimensional ( 1D ) and hydrostatic , and by ignoring departures from local thermodynamic equilibrium ( LTE ) .
In order to address this , we carried out three-dimensional ( 3D ) non-LTE radiative transfer calculations for C I and O I , and 3D LTE radiative transfer calculations for Fe II , across the stagger -grid of 3D hydrodynamic model atmospheres .
The absolute 3D non-LTE versus 1D LTE abundance corrections can be as severe as -0.3 \mathrm { dex } for C I lines in low-metallicity F dwarfs , and -0.6 \mathrm { dex } for O I lines in high-metallicity F dwarfs .
The 3D LTE versus 1D LTE abundance corrections for Fe II lines are less severe , typically less than +0.15 \mathrm { dex } .
We used the corrections in a re-analysis of carbon , oxygen , and iron in 187 F and G dwarfs in the Galactic disk and halo .
Applying the differential 3D non-LTE corrections to 1D LTE abundances visibly reduces the scatter in the abundance plots .
The thick disk and high- \upalpha halo population rise in carbon and oxygen with decreasing metallicity , and reach a maximum of \mathrm { \left [ C / Fe \right ] } \approx 0.2 and a plateau of \mathrm { \left [ O / Fe \right ] } \approx 0.6 at \mathrm { \left [ Fe / H \right ] } \approx - 1.0 .
The low- \upalpha halo population is qualitatively similar , albeit offset towards lower metallicities and with larger scatter .
Nevertheless , these populations overlap in the \mathrm { \left [ C / O \right ] } versus \mathrm { \left [ O / H \right ] } plane , decreasing to a plateau of \mathrm { \left [ C / O \right ] } \approx - 0.6 below \mathrm { \left [ O / H \right ] } \approx - 1.0 .
In the thin-disk , stars having confirmed planet detections tend to have higher values of \mathrm { C / O } at given \mathrm { \left [ O / H \right ] } ; this potential signature of planet formation is only apparent after applying the abundance corrections to the 1D LTE results .
Our grids of line-by-line abundance corrections are publicly available and can be readily used to improve the accuracy of spectroscopic analyses of late-type stars .