对APOGEE数据的分析表明，在[ $α$ /Fe]与[Fe/H]丰度比空间中，两个盘星序列之间存在着明显的区别。我们的目标是测试，如果两个落入化学演化模型设计，以再现这两个序列在太阳附近也能够预测光盘双峰观察到的垂直分布的[Mg/Fe]在APOGEE DR 16数据。随着预测的化学成分的SSP出生在不同的银河系时间在太阳附近，我们提供了它们的最大垂直高度|zmax|以上的银河系平面计算假设之间的关系，在薄盘星的垂直行动和恒星年龄。预测的[Mg/Fe]丰度比的垂直分布与结合APOGEE DR 16数据和astroNN目录（恒星年龄，轨道参数）的年龄小于8 Gyr的恒星（仅低- $α$序列星）观察到的一致。包括高$α$盘组件，在垂直的[Mg/Fe]丰度分布的二分法再现考虑到观测切割的银河系高度|z| < 2千秒差距。然而，我们的模型预测的|zmax|作为[Mg/Fe]的函数的高$α$对象在从APOGEE数据的中值相比，过于平坦的增长。对这种张力的可能解释是：i）|z| < 2 kpc的数据样本更有可能被晕星污染，导致中间值在运动学上更热，ii）外部扰动，如微小的合并可能会加热圆盘，轨道的加热不能仅用散射过程来模拟。假设数据是基于化学的椎间盘解剖，如果我们在计算中考虑垂直作用估计的误差，则观察到的高$α$和低$α$序列的|zmax|分布与我们的模型预测吻合良好。
英文摘要：
The analysis of the APOGEE data suggests the existence of a clear distinction between two sequences of disc stars in the [$α$/Fe] vs. [Fe/H] abundance ratio space. We aim to test if the two-infall chemical evolution models designed to reproduce these two sequences in the solar neighbourhood are also capable to predict the disc bimodality observed in the vertical distribution of [Mg/Fe] in APOGEE DR16 data. Along with the predicted chemical composition of SSPs born at different Galactic times in the solar vicinity, we provide their maximum vertical height |zmax| above the Galactic plane computed assuming the relation between the vertical action and stellar age in thin disc stars. The predicted vertical distribution of the [Mg/Fe] abundance ratio is in agreement with the one observed combining the APOGEE DR16 data and the astroNN catalogue (stellar ages, orbital parameters) for stars younger than 8 Gyr (only low-$α$ sequence stars). Including the high-$α$ disc component, the dichotomy in the vertical [Mg/Fe] abundance distribution is reproduced considering the observational cut in the Galactic height of |z| < 2 kpc. However, our model predicts a too flat growth of the |zmax| as a function of [Mg/Fe] for high-$α$ objects in contrast with the median values from APOGEE data. Possible explanations for such a tension are: i) the data sample with |z| < 2 kpc is more likely contaminated by halo stars, causing the median values to be kinematically hotter, ii) external perturbations such as minor mergers could have heated up the disc, and the heating of the orbits cannot be modelled by only scattering processes. Assuming for the data a disc dissection based on chemistry, the observed |zmax| distributions for high-$α$ and low-$α$ sequences are in good agreement with our model predictions if we consider in the calculation the errors in the vertical action estimates.
Co-evolution of the Milky Way high- and low-α sequences with chemical evolution models
INAF, Osservatorio Astronomico di Trieste（意大利国家天体物理研究所，的里雅斯特天文台）；IFPU, Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；Dipartimento di Fisica, Sezione di Astronomia, Università di Trieste（的里雅斯特大学，物理系，天文学部）；INFN Sezione di Trieste（意大利国家核物理研究所，的里雅斯特分部）
本文通过改进的化学演化模型探讨银河盘内高α和低α序列的共同演化及古老低α星的存在，解释了观测到的[α/Fe] vs [Fe/H]图谱。
The Two-infall Model Revisited: Constraints on Milky Way Bulge Assembly from >30,000 Galactic Chemical Evolution Models and Machine Learning
University of Wyoming（怀俄明大学）；Space Telescope Science Institute（太空望远镜科学研究所）；Department of Astronomy, University of Florida（佛罗里达大学天文学系）；University of Bayreuth（拜罗伊特大学）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与教育网络地球与天文学研究中心）；CSFK, MTA Centre of Excellence（CSFK，匈牙利科学院卓越中心）；Department of Physics and Astronomy, UCLA（加州大学洛杉矶分校物理与天文学系）
Portrait of a Galaxy on FIRE: Is the $α$-bimodality a natural consequence of inside-out disc growth in a hierarchical formation scenario?
Tartu Observatory, University of Tartu（塔尔图大学塔尔图天文台）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；Tallinn University of Technology（塔林理工大学）
A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE): XVI. The ubiquity of truncated star-forming disks across the Virgo cluster environment
