论文标题
与盖亚（Gaia）的群集的运动学建模：羟基的死亡喉咙
Kinematic modelling of clusters with Gaia: the Death Throes of the Hyades
论文作者
论文摘要
GAIA数据的精度为研究星团的内部速度场提供了独特的机会。我们为群集中恒星的内部运动开发并验证一种前向模型方法。该模型允许各向异性速度分散矩阵和线性速度梯度描述旋转和剪切，结合了可用于恒星子集的径向速度，并通过混合模型对背景来源污染。我们将方法应用于Hyades群集及其潮汐尾的Gaia DR2数据，对恒星在10 pc之内和超过10 pc之内进行了分裂和比较，这大约是簇的潮汐半径。尽管簇的速度分散量几乎是各向同性的，但尾部的速度椭圆形显然伸长，主要轴指向银河系中心。我们发现在$ \ \ \ \2σ$上的正膨胀在银河方位面和垂直方向上的显着性，但没有旋转。潮汐尾巴朝着从银河中心倾斜的方向拉伸，同时收缩与银河垂直方向的簇相同。尾巴的剪切（a）为$ 16.90 \ pm 0.92 $ m/s/pc，涡度（b）为$ -6.48 \ pm1.15 $ m/s/pc，值与本地Oort常数不同。
The precision of the Gaia data offers a unique opportunity to study the internal velocity field of star clusters. We develop and validate a forward-modelling method for the internal motions of stars in a cluster. The model allows an anisotropic velocity dispersion matrix and linear velocity gradient describing rotation and shear, combines radial velocities available for a subset of stars, and accounts for contamination from background sources via a mixture model. We apply the method to Gaia DR2 data of the Hyades cluster and its tidal tails, dividing and comparing the kinematics of stars within and beyond 10 pc, which is roughly the tidal radius of the cluster. While the velocity dispersion for the cluster is nearly isotropic, the velocity ellipsoid for the tails is clearly elongated with the major axis pointing towards the Galactic centre. We find positive and negative expansion at $\approx 2σ$ significance in Galactic azimuthal and vertical direction for the cluster but no rotation. The tidal tails are stretching in a direction tilted from the Galactic centre while equally contracting as the cluster in Galactic vertical direction. The tails have a shear (A) of $16.90\pm 0.92$ m/s/pc and a vorticity (B) of $-6.48\pm1.15$ m/s/pc, values distinct from the local Oort constants.
