Chemical composition of open clusters. I - Fe/H from high-resolution spectroscopy. II - C/H and C/Fe in F dwarfs from high-resolution spectroscopy

Using high-resolution spectroscopy, the abundance ratios Fe/H, C/H, and C/Fe were determined for F dwarfs in the Alpha Per, the Pleiades, and the Hyades clusters; the UMa, Hyades, and Wolf 630 moving groups; and a selection of bright F field dwarfs. The age span of these objects ranges from 5 x 10 to the 7th to 2 x 10 to the 9th yr. No evidence was found of a trend in Fe/H with age for these clusters and groups, but there were clear differences in Fe/H among these groups, indicating intrinsic differences in the metal content of the local gas out of which these groups were formed. No evidence was found for a trend of C/H with age of these stellar groups, but there were cluster-to-cluster variations, implying differences in the content of carbon in the precluster gas. The C/H cluster differences followed the same pattern as the Fe/H cluster differences and yield C/Fe values which are constant, and equal to the solar value, in all the groups.