发表机构
Instituto de Astrofísica de Canarias; Universidad de La Laguna; Universidad de Granada（加那利天体物理研究所; 拉古纳大学; 格拉纳达大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用盖亚数据CMD拟合获得精确年龄，发现银河系盘标高下降速率在约10.85 Gyr前剧变，支持厚盘快速形成与薄盘缓慢沉降的两阶段演化模型。
AI 中文摘要
银河系盘恒星在不同年龄和金属丰度下的空间分布编码了其动力学演化历史和形成路径。传统上，缺乏大规模代表性恒星样本的精确年龄一直是可靠区分解释银河系盘垂直特性的形成机制（例如上下颠倒形成与长期动力学加热）的障碍。在本信中，我们利用盖亚数据的CMD拟合，为太阳邻域完整恒星样本导出了非常精确的年龄-金属丰度分布。我们识别出年龄分辨率优于5%（在老年时约0.5 Gyr）的准单一年龄-金属丰度恒星群体，并研究其绝对垂直密度轮廓。我们观察到标高与恒星年龄之间存在明显相关性，较年轻的群体更一致地局限于盘面。我们发现标高下降速率在10.85^{+0.13}_{-0.12} Gyr前发生了剧烈变化的证据：在更老的年龄，演化非常陡峭，h_Z在仅2 Gyr内从超过1.26 kpc下降到约0.5 kpc；随后，变薄非常缓慢，最年轻群体的h_Z约为0.1 kpc。盘早期极快速的垂直沉降指向早期根本上上下颠倒的形成过程，此时厚盘成分基本形成。因此，我们强烈支持由两个不同时间阶段定义的演化场景：一个初始的高湍流时期孕育了厚盘，以及随后的更平静的长期演化和气体逐渐沉降时期形成了薄盘。
英文摘要
The spatial distribution of Galactic disk stars of different ages and metallicities encodes its dynamical evolution history and formation pathways. The lack of precise ages for large, representative samples of stars has traditionally been a drawback for securely differentiating among formation scenarios proposed to explain the vertical properties of the Milky Way disk (e.g. upside-down formation versus secular dynamical heating). In this Letter, we use CMD-fitting of Gaia data to derive very precise age-metallicity distributions for complete stellar samples in the solar neighborhood. We identify quasi-mono-age-metallicity stellar populations with an age resolution better than $5 \%$ ($\sim 0.5$ Gyr at old age), and study their absolute vertical density profile. We observe a clear correlation between scale height and stellar age, with younger populations consistently more confined to the plane. We find evidence that the scale height decrease rate changed drastically $10.85^{+0.13}_{-0.12}$ Gyr ago: at older ages, the evolution is very steep, with $h_Z$ dropping from over $1.26$ kpc to $\sim 0.5$ kpc in merely $2$ Gyr; subsequently, the thinning is very gradual, with $h_Z \sim 0.1$ kpc for the youngest populations. The extremely rapid early vertical settling of the disk points to a fundamentally upside-down formation process at early times, when the thick disk component is basically formed. We thus strongly support an evolutionary scenario defined by two distinct temporal phases: an initial, highly turbulent epoch that gave birth to the thick disk, and a subsequent more quiescent period of secular evolution and gradual gas settling which formed the thin disk.
Comments17 pages, 10 figures, accepted for publication in ApJL
