In order to trace the origin and evolution of carbon in the Galactic disk we have determined carbon abundances in 51 nearby F and G dwarf stars .
The sample is divided into two kinematically distinct subsamples with 35 and 16 stars that are representative of the Galactic thin and thick disks , respectively .
The analysis is based on spectral synthesis of the forbidden [ C i ] line at 872.7 nm using spectra of very high resolution ( R \approx 220 000 ) and high signal-to-noise ( S / N \gtrsim 300 ) that were obtained with the CES spectrograph on the ESO 3.6-m telescope on La Silla in Chile .
We find that [ C/Fe ] versus [ Fe/H ] trends for the thin and thick disks are totally merged and flat for sub-solar metallicities .
The thin disk that extends to higher metallicities than the thick disk , shows a shallow decline in [ C/Fe ] from [ Fe / H ] \approx 0 and up to [ Fe / H ] \approx + 0.4 .
The [ C/O ] versus [ O/H ] trends are well separated between the two disks ( due to differences in the oxygen abundances ) and bear a great resemblance to the [ Fe/O ] versus [ O/H ] trends .
Our interpretation of our abundance trends is that the sources that are responsible for the carbon enrichment in the Galactic thin and thick disks have operated on a time-scale very similar to those that are responsible for the Fe and Y enrichment ( i.e. , SN Ia and AGB stars , respectively ) .
We further note that there exist other observational data in the literature that favour massive stars as the main sources for carbon .
In order to match our carbon trends , we believe that the carbon yields from massive stars then must be very dependent on metallicity for the C , Fe , and Y trends to be so finely tuned in the two disk populations .
Such metallicity dependent yields are no longer supported by the new stellar models in the recent literature .
For the Galaxy we hence conclude that the carbon enrichment at metallicities typical of the disk is mainly due to low and intermediate mass stars , while massive stars are still the main carbon contributor at low metallicities ( halo and metal-poor thick disk ) .