The Geneva-Copenhagen Survey of the Solar neighbourhood II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk - AstrophysicsReportar como inadecuado




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Abstract: Ages, metallicities, space velocities, and Galactic orbits of stars in theSolar neighbourhood are fundamental observational constraints on models ofgalactic disk evolution. We aim to consolidate the calibrations of uvbyphotometry into Te, Fe-H, distance, and age for F and G stars and rediscussthe results of the Geneva-Copenhagen Survey Nordstrom et al. 2004; GCS interms of the evolution of the disk.We substantially improve the Te and Fe-H calibrations for early F stars,where spectroscopic temperatures have large systematic errors. Our recomputedages are in excellent agreement with the independent determinations by Takedaet al. 2007, indicating that isochrone ages can now be reliably determined.The revised G-dwarf metallicity distribution remains incompatible withclosed-box models, and the age-metallicity relation for the thin disk remainsalmost flat, with large and real scatter at all ages sigma intrinsic = 0.20dex. Dynamical heating of the thin disk continues throughout its life;specific in-plane dynamical effects dominate the evolution of the U and Vvelocities, while the W velocities remain random at all ages. When assigningthick and thin-disk membership for stars from kinematic criteria, parametersfor the oldest stars should be used to characterise the thin disk.



Autor: J. Holmberg, B. Nordstrom, J. Andersen

Fuente: https://arxiv.org/







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