The eye of Gaia on globular clusters kinematics: internal rotation
  We derived the three-dimensional velocities of individual stars in a sample
of 62 Galactic globular clusters using proper motions from the second data
release of the Gaia mission together with the most comprehensive set of
line-of-sight velocities with the aim of investigating the rotation pattern of
these stellar systems. We detect the unambiguous signal of rotation in 15
clusters at amplitudes which are well above the level of random and systematic
errors. For these clusters, we derived the position and inclination angle of
the rotation axis with respect to the line of sight and the overall
contribution of rotation to the total kinetic energy budget. The rotation
strengths are weakly correlated with the half-mass radius, the relaxation time
and anticorrelated with the destruction rate, while no significant alignment of
the rotation axes with the orbital poles has been observed. This evidence
points toward a primordial origin of the systemic rotation in these stellar
systems.
