基于LAMOST红巨星样本研究银盘化学动力学性质随时间的演化

Understanding the formation and evolution of the galactic disk is one of the most vital problems in the field of galaxy formation and evolution. As our host galaxy, the Milky Way is a typical disk galaxy and is also the only galactic disk whose individual stars can be fully resolved. A detailed characterizing for the structure and chemo-dynamic properties of the Galactic disk is thus of vital importance to understand the formation and evolution of galactic disk(s). In recent years, a series of space high-precision photometry surveys and ground large-scale spectral surveys provides significant opportunities for studying the chemo-dynamic properties of the Galactic disk. Currently, the LAMOST DR4 have obtained more than 6.5 million stellar spectra, including 0.89 million RGB stellar spectra. In this project, we plan to obtain a large sample of LAMOST RGB stars with reliable age estimates utilizing the machine learning method. Wtih this sample, we cross-match them with Gaia DR2 and obtain their kinematic parameters, then we further study the correlations between age, kinematics, and metallicity, understand the orgin of young stars with high alpha and old stars with high metallicity in the sample, thus to better understand the formation and evolution of the Galactic disk.

理解星系盘的形成和演化是目前星系形成与演化领域的核心问题之一。银河系作为我们的寄主星系，是一个典型的盘状星系，也是唯一一个我们能够分辨大样本单颗恒星的星系，研究其化学动力学性质对于理解星系盘的形成和演化具有重要意义。近年来，一系列空间高精度测光巡天和地面大规模光谱巡天的开展为研究银河系化学动力学性质随时间的演化提供了重要的机会。LAMOST第四期已经获得了超过650万条光谱，其中红巨星光谱有89万条。本项目计划基于LAMOST光谱利用机器学习方法估计红巨星较为精确的质量和年龄，并与Gaia第二期释放的数据交叉，获得它们的运动学参数，构建具有精确年龄和质量估计以及三维位置、三维速度和元素丰度信息的大规模银盘红巨星样本，并利用该样本研究金属丰度与运动学参数随时间的演化；利用该样本，针对样本中的奇异恒星，理解其起源问题，进而理解银盘的形成与演化历史。

本项目利用LAMOST一期正式巡天的海量数据，结合其他巡天（Gaia）数据，致力于研究银盘化学动力学随时间的演化。通过本项目的实施，增强对银盘形成机制的理解。利用具有精确年龄和质量测量的LAMOST红巨星样本与Gaia数据结合，描绘银盘恒星三维的速度，弥散，偏度等参数在年龄-金属丰度空间以及R-Z空间的变化，探讨了恒星的迁移对薄盘恒星的影响；基于LAMOST红巨星样本中“奇异”恒星（年轻高alpha恒星和年老富金属恒星），通过研究元素丰度信息，探究其起源问题。