Chemical constraints on the formation of the Galactic thick disk
  We highlight some results from our detailed abundance analysis study of 703
kinematically selected F and G dwarf stars in the solar neighbourhood. The
analysis is based on spectra of high-resolution (R=45000 to 110000) and high
signal-to-noise (S/N=150 to 300). The main findings include: (1) at a given
metallicity, the thick disk abundance trends are more $\alpha$-enhanced than
those of the thin disk; (2) the metal-rich limit of the thick disk reaches at
least solar metallicities; (3) the metal-poor limit of the thin disk is around
[Fe/H]=-0.8; (4) the thick disk shows an age-metallicity gradient; (5) the thin
disk does {\it not} show an age-metallicity gradient; (6) the most metal-rich
thick disk stars at [Fe/H]=0 are significantly older than the most metal-poor
thin disk stars at [Fe/H]=-0.7; (7) based on our elemental abundances we find
that kinematical criteria produce thin and thick disk stellar samples that are
biased in the sense that stars from the low-velocity tail of the thick disk are
classified as thin disk stars, and stars from the high-velocity tail of the
thin disk are classified as thick disk stars; (8) age criteria appears to
produce thin and thick disk stellar samples with less contamination.
