基于LAMOST及Gaia巡天数据的银河系质量及其分布的精确测量

An accurate determination of the mass distribution of the Milky Way is of vital importance for understanding the Galaxy formation and evolution and testing the standard cosmological model, particle physics and gravitation theory. The nearly ten million quality stellar spectra collected (accumulated) hitherto by the LAMOST Galactic Spectroscopic Surveys, together with the accurate parallaxes and proper motions from the ESA Gaia astrometric survey, provide a great opportunity to accurately measure the gravitational potential and mass distribution (both of baryonic and dark matter) of the Milky Way..By combining the data from the LAMOST and Gaia surveys, we aim to construct value-added catalogues of multi-dimensional parameters of unprecedented precision for huge numbers of stars and of featured samples of halo tracers. Using the data, we propose to tackle the following problems: 1) Accurate determination of the Galactic rotation curve out to r ~ 100 kpc; 2) Accurate determination of the Galactic escape velocity curve within r ~ 20 kpc; 3) Identifying member stars of kinematically cold stellar streams and using their phase space (3D position plus velocity) information to constrain the shape of the Galactic dark matter halo; 4) Searching for hypervelocity stars and using their kinematic information to explore the Galactic gravitational potential. Based on the above studies, we aim to accurately map the mass distributions of both the dark and baryonic matter of the Milky Way and achieve an accurate measurement of the Galactic total mass.

精确测定银河系质量及其分布对理解银河系的形成和演化，检验标准宇宙模型、粒子物理和引力理论至关重要。LAMOST光谱巡天获得的近千万条恒星光谱以及Gaia天测巡天提供的精确恒星距离和自行为银河系引力势及物质分布的精确测定提供了历史性机遇。本项目拟结合LAMOST与Gaia巡天数据构建包含海量恒星高精度多维相空间信息的增值星表以及挑选针对银晕研究的特色样本，开展以下几方面研究：1）测定银河系远至百kpc的高精度旋转曲线；2）测定银河系20kpc内的逃逸速度曲线；3）证认银河系中（运动学上）较冷星流的成员星并利用它们的相空间信息（三维位置和三维速度）限制暗物质晕的形状；4）搜索超高速星并利用它们的运动学信息限制银河系引力势。通过上述研究，最终细致描绘出暗物质和重子物质的质量分布，给出准确的银河系质量分布，精确测定银河系的总质量。

作为银河系最基本的物理参数之一，银河系质量及其分布的测量一直是当代天文学的前沿热点问题之一。为取得高精度的银河系质量测量，本项目基于LAMOST释放的海量光谱数据和Gaia天测卫星释放的数十亿颗恒星高精度天测信息，遴选了一批优良的银河系示踪物，测量了视向速度、元素丰度和距离等关键参数，构建了具有三维位置、三维速度等在内的高精度多维向空间信息的海量恒星增值星表，开展了以下几方面研究：1）搜寻并构建了目前最大的（超）高速星样本，为后续测定银河系逃逸速度曲线的奠定了坚实基础；2）精细刻画了银盘的结构、化学及运动学性质；3）细致研究银晕的整体结构和子结构及其演化；4）测定了目前最为精确的银河系旋转曲线，基于该曲线限定了银河系总质量及其分布。