Carbon and oxygen abundances in F and G main-sequence stars ranging in metallicity from [ Fe/H ] = -1.6 to +0.5 are determined from a non-LTE analysis of C i and O i atomic lines in high-resolution spectra .
Both C and O are good tracers of stellar populations ; distinct trends of [ C/Fe ] and [ O/Fe ] as a function of [ Fe/H ] are found for high- and low-alpha halo stars and for thick- and thin-disk stars .
These trends and that of [ C/O ] provide new information on the nucleosynthesis sites of carbon and the time-scale for the chemical enrichment of the various Galactic components .