We investigate the stellar kinematics of the Galactic disc in 7 < R < 13 kpc using a sample of 118 945 red giant branch (RGB) stars from LAMOST and Gaia. We characterize the median, dispersion and skewness of the distributions of the 3D stellar velocities, actions and orbital parameters across the age-metallicity and the disc R – Z plane. Our results reveal abundant but clear stellar kinematic patterns and structures in the age – metallicity and the disc R – Z plane. The most prominent feature is the strong variations of the velocity, action, and orbital parameter distributions from the young, metal-rich thin disc to the old, metal-poor thick disc, a number of smaller-scale structures — such as velocity streams, north-south asymmetries, and kinematic features of spiral arms — are clearly revealed. Particularly, the skewness of Vφ and Jφ reveals a new substructure at R ' 12 kpc and Z ' 0 kpc, possibly related to dynamical effects of spiral arms in the outer disc. We further study the stellar migration through analysing the stellar orbital parameters and stellar birth radii. The results suggest that the thick disc stars near the solar radii and beyond are mostly migrated from the inner disc of R ∼ 4 − 6 kpc due to their highly eccentrical orbits. Stellar migration due to dynamical processes with angular momentum transfer (churning) are prominent for both the old, metal-rich stars (outward migrators) and the young metal-poor stars (inward migrators). The spatial distribution in the R – Z plane for the inward migrators born at a Galactocentric radius of >12 kpc show clear age stratifications, possibly an evidence that these inward migrators are consequences of splashes triggered by merger events of satellite galaxies that have been lasted in the past few giga years.

中文翻译：

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来自 LAMOST 和 Gaia 的银河系盘的年龄-金属性相关恒星运动学

我们使用来自 LAMOST 和 Gaia 的 118 945 颗红巨星分支 (RGB) 恒星的样本研究了银河盘在 7 < R < 13 kpc 内的恒星运动学。我们描述了 3D 恒星速度、活动和轨道参数在年龄金属量和圆盘 R-Z 平面上分布的中值、色散和偏度。我们的结果揭示了该时代丰富但清晰的恒星运动模式和结构——金属丰度和圆盘 R-Z 平面。最突出的特征是速度、作用力和轨道参数分布的强烈变化，从年轻的、富含金属的薄盘到旧的、贫金属的厚盘、许多较小尺度的结构——例如速度流、南北不对称，以及旋臂的运动学特征——都被清楚地揭示出来。特别，Vφ 和 Jφ 的偏度揭示了 R ' 12 kpc 和 Z ' 0 kpc 处的新子结构，可能与外盘中螺旋臂的动力学效应有关。我们通过分析恒星轨道参数和恒星诞生半径来进一步研究恒星迁移。结果表明，靠近太阳半径及更远的厚盘星由于其高度偏心的轨道，大多是从 R ∼ 4 − 6 kpc 的内盘迁移的。由于具有角动量转移（搅动）的动力学过程导致的恒星迁移对于年老的富含金属的恒星（向外迁移者）和年轻的贫金属恒星（向内迁移者）都很突出。出生于半乳中心半径大于 12 kpc 的向内迁移者在 R-Z 平面的空间分布显示出明显的年龄分层，