150万颗LAMOST恒星的群体动力学年龄

中文摘要 AI 辅助

我们提出了一种框架，用于从光谱学恒星参数推断恒星年龄，该框架通过平均相似大气和化学性质恒星的中位垂直作用$J_z$来校准群体动力学，从而在赫罗图上获得自洽的年龄估计。我们称这些年龄为群体动力学年龄，因为年龄尺度是通过具有相似恒星参数恒星群体的平均动力学来校准的。在分配年龄时不使用单个恒星的动力学。我们通过次巨星年龄验证了该方法，其准确性约为30%，与[C/N]基于估计相当。我们发现了一个清晰的年龄-$J_z$关系，使高-低α盘的年龄推断可达约100亿年。将此框架应用于150万颗LAMOST恒星，我们推导出次巨星和巨星的年龄，典型不确定度约为20亿年。推导出的年龄与文献年龄目录一致，无显著的$\log g$函数系统趋势。我们还展示了经验等时线校准理论恒星模型的潜力。我们识别出低α盘中一个老(~70亿年)的群体，但未得出明确结论。尽管群体动力学年龄是统计的，对选择效应、银河潜在假设和银河位置敏感，但它们为银河考古提供了一种稳健的群体层面工具，补充了传统年龄指标，并扩展了整个赫罗图的年龄估计。

英文摘要

We present a framework for inferring stellar ages from spectroscopic stellar parameters, calibrated with ensemble kinematics by averaging over the median vertical action, $J_z$, for stars with similar atmospheric and chemical properties, yielding self-consistent age estimates across the Hertzsprung-Russell (HR) diagram. We refer to these ages as ensemble kinematic ages as the age scale is calibrated from the average kinematics of ensembles of stars with similar stellar parameters. Individual stellar kinematics are not used in assigning ages. We validate the method against subgiant ages, achieving an accuracy of ~30%, comparable to [C/N]-based estimates. We find a clear age-$J_z$ relations that enable age inference up to ~10 Gyr for both the high- and low-$α$ disks. Applying this framework to 1.5 million LAMOST stars, we derive ages for subgiants and giants with typical uncertainties of ~2 Gyr. The inferred ages agree well with literature age catalogs, with no significant systematic trends as a function of $\log g$. We also demonstrate the potential of empirical isochrones to calibrate theoretical stellar models. We identify an old (~7 Gyr) population within the low-$α$ disk but draw no firm conclusions. Although ensemble kinematic ages are statistical and sensitive to selection effects, Galactic potential assumptions, and Galactic location, they provide a robust population-level tool for Galactic archaeology, complementing traditional age indicators and extending age estimates across the full HR diagram.

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Submitted to AJ