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arXiv 0707.1891astro-ph
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日内瓦-哥本哈根太阳邻域巡天II。恒星年龄、G矮星问题、年龄-金属丰度图和盘加热机制的新UVBY校准和再讨论

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

J. Holmberg, B. Nordstrom, J. Andersen

摘要:

年龄,金属丰度,空间速度,和银河系轨道的恒星在太阳附近的银河系盘演化模型的基本观测约束。我们的目标是巩固校准的紫外线光度到Te,[Fe/H],距离和年龄的F和G星和重新讨论的结果,日内瓦-哥本哈根调查(Nordstrom等。2004年; GCS)的演变方面的磁盘。我们大大提高了早期F星的Te和[Fe/H]校准,光谱温度有很大的系统误差。我们重新计算的年龄与Takeda等人(2007)的独立测定结果非常一致,表明现在可以可靠地测定等时线年龄。修订后的G-矮星金属丰度分布仍然与闭箱模型不兼容,薄盘的年龄-金属丰度关系几乎保持平坦,在所有年龄都有大的真实分散(σ内在= 0.20 dex)。薄盘的动态加热在其整个生命周期中持续;特定的面内动力学效应主导U和V速度的演化,而W速度在所有年龄段都保持随机。当从运动学标准为恒星分配厚盘和薄盘成员时,最老恒星的参数应该用来确定薄盘。

英文摘要:

Ages, metallicities, space velocities, and Galactic orbits of stars in the Solar neighbourhood are fundamental observational constraints on models of galactic disk evolution. We aim to consolidate the calibrations of uvby photometry into Te, [Fe/H], distance, and age for F and G stars and rediscuss the results of the Geneva-Copenhagen Survey (Nordstrom et al. 2004; GCS) in terms 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 recomputed ages are in excellent agreement with the independent determinations by Takeda et al. (2007), indicating that isochrone ages can now be reliably determined. The revised G-dwarf metallicity distribution remains incompatible with closed-box models, and the age-metallicity relation for the thin disk remains almost flat, with large and real scatter at all ages (sigma intrinsic = 0.20 dex). Dynamical heating of the thin disk continues throughout its life; specific in-plane dynamical effects dominate the evolution of the U and V velocities, while the W velocities remain random at all ages. When assigning thick and thin-disk membership for stars from kinematic criteria, parameters for the oldest stars should be used to characterise the thin disk.

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