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arXiv 2004.14806astro-ph.GAastro-ph.SR
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Milky Way盘的年龄解剖：开普勒场中的红巨星

Age dissection of the Milky Way discs: red giants in the Kepler field

Andrea Miglio, Cristina Chiappini, Ted Mackereth, Guy Davies, Karsten Brogaard, Luca Casagrande, Bill Chaplin, Leo Girardi, Daisuke Kawata, Saniya Khan, Rob Izz… 展开作者

Andrea Miglio, Cristina Chiappini, Ted Mackereth, Guy Davies, Karsten Brogaard, Luca Casagrande, Bill Chaplin, Leo Girardi, Daisuke Kawata, Saniya Khan, Rob Izzard, Josefina Montalban, Benoit Mosser, Fiorenzo Vincenzo, Diego Bossini, Arlette Noels, Thaise Rodrigues, Marica Valentini, Ilya Mandel

备注：
accepted for publication in A&A, 26 pages, 24 figures, catalogue available via cds
发表信息：
A&A 645, A85 (2021)
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摘要：

对红巨星的环绕研究具有精致的星震，光谱和天体测量的限制，提供了一个新的机会来重铸和解决有关恒星和银河系演化的长期问题。在这里，我们推断质量和年龄的近5400巨星可用开普勒光变曲线和APOGEE光谱，并讨论了一些可能会影响推断的恒星性质的准确性的系统学。首先，我们来看看年龄-化学-丰度的关系。我们发现缺乏年轻的，富含金属的恒星，和存在一个显着的人口的老（8-9 Gyr），低[ $α$ /Fe]，超太阳的金属丰度恒星，让人想起的年龄和金属丰度的研究疏散星团NGC 6791。这些恒星的年龄-化学-运动学性质表明，有效的径向迁移发生在薄盘。我们发现，在我们的样本中，近400颗富含$α$元素的红巨星分支（RGB）恒星的年龄和质量与一个古老的（~11 Gyr），几乎同时代的，化学厚的磁盘人口是兼容的。使用统计模型，我们发现，95%的人口出生在~1.5 Gyr。此外，我们发现低和高[ $α$ /Fe]人口之间的垂直速度色散的差异，确认他们不同的化学动力学的历史。然后，我们利用几乎同时代的$α$丰富的人口，以深入了解过程中，可能已经改变了恒星的质量沿其演变，这是关键，以改善所观察到的恒星质量的年龄映射。我们发现的证据表明，平均综合RGB质量损失< $Δ$ M>= 0.10 $\pm$ 0.02 Msun和发生的大规模（M $\gtrsim$ 1.1 Msun）$α$丰富的恒星是RGB的顺序为5%，并显着更高的RC，支持的情况下，大多数这些恒星经历了与同伴的相互作用。

英文摘要：

[Abridged] Ensemble studies of red-giant stars with exquisite asteroseismic, spectroscopic, and astrometric constraints offer a novel opportunity to recast and address long-standing questions concerning the evolution of stars and of the Galaxy. Here, we infer masses and ages for nearly 5400 giants with available Kepler light curves and APOGEE spectra, and discuss some of the systematics that may affect the accuracy of the inferred stellar properties. First, we look at age-chemical-abundances relations. We find a dearth of young, metal-rich stars, and the existence of a significant population of old (8-9 Gyr), low-[$α$/Fe], super-solar metallicity stars, reminiscent of the age and metallicity of the well-studied open cluster NGC6791. The age-chemo-kinematic properties of these stars indicate that efficient radial migration happens in the thin disk. We find that ages and masses of the nearly 400 $α$-element-rich red-giant-branch (RGB) stars in our sample are compatible with those of an old (~11 Gyr), nearly coeval, chemical-thick disk population. Using a statistical model, we show that 95% of the population was born within ~1.5 Gyr. Moreover, we find a difference in the vertical velocity dispersion between low- and high-[$α$/Fe] populations, confirming their different chemo-dynamical histories. We then exploit the almost coeval $α$-rich population to gain insight into processes that may have altered the mass of a star along its evolution, which are key to improve the mapping of the observed stellar mass to age. We find evidence for a mean integrated RGB mass loss <$Δ$M>= 0.10 $\pm$ 0.02 Msun and that the occurrence of massive (M $\gtrsim$ 1.1 Msun) $α$-rich stars is of the order of 5% on the RGB, and significantly higher in the RC, supporting the scenario in which most of these stars had undergone interaction with a companion.

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