Geneva-Copenhagen survey re-analysis

Metallicities are calibrated on high-resolution spectroscopy and checked against four open clusters and a moving group, showing excellent consistency. The new temperature and metallicity scales provide a better match to theoretical isochrones, which are used for a Bayesian analysis of stellar ages.

With respect to previous analyses, our stars are on average 100K hotter and 0.1dex more metal rich, shifting the peak of the metallicity distribution function around the solar value. From Stromgren photometry we are able to derive for the first time a proxy for [Fe] abundances, which enables for a tentative dissection of the chemical thin and thick disc. We find evidence for the latter being composed of an old, mildly but systematically alpha-enhanced population extending to super solar metallicities, in agreement with spectroscopic studies.