Kinematic modelling of clusters with Gaia: the Death Throes of the Hyades

Understand

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.