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Symposium 241

Abstract details

Evolution of the Local Galactic Disk
Johan Holmberg, Birgitta Nordström, and Johannes Anderssen

The ages, metallicities, velocities, and Galactic orbits of stars in the Solar neighbourhood are fundamental constraints on models of the evolution of galactic disks. They are derived from the observational data through a variety of calibrations, which may introduce systematic errors in the results. Understanding and minimising such errors and their interaction with selection biases in the sample is fundamental for the interpretation. We aim to verify and/or improve the calibrations of Strömgren photometry into Teff and [Fe/H] for F and G stars, and re-check their effect on the derived ages. Using a large body of published V-K photometry and high-resolution spectroscopy, we derive new significantly improved temperatures and metallicities, which then result in much more accurate ages when combined with empirically corrected isochrones. The robustness of the derived relations is verified by extensive numerical simulations. We then revisit the salient results of the Geneva-Copenhagen Survey of the Solar Neighbourhood (Nordström et al. 2004), the largest and least-biased complete sample of nearby long-lived stars. This includes the G-dwarf metallicity distribution, the age-metallicity relation for the thin and thick disk and the kinematic evolution of the disk.

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