Using Gaia for studying Milky Way star clusters
  We review the implications of the Gaia Data Release 2 catalogue for studying
the dynamics of Milky Way globular clusters, focusing on two separate topics.
The first one is the analysis of the full 6-dimensional phase-space
distribution of the entire population of Milky Way globular clusters: their
mean proper motions (PM) can be measured with an exquisite precision (down to
0.05 mas/yr, including systematic errors). Using these data, and a suitable
ansatz for the steady-state distribution function (DF) of the cluster
population, we then determine simultaneously the best-fit parameters of this DF
and the total Milky Way potential. We also discuss possible correlated
structures in the space of integrals of motion. The second topic addresses the
internal dynamics of a few dozen of the closest and richest globular clusters,
again using the Gaia PM to measure the velocity dispersion and internal
rotation, with a proper treatment of spatially correlated systematic errors.
Clear rotation signatures are detected in 10 clusters, and a few more show
weaker signatures at a level >=0.05$ mas/yr. PM dispersion profiles can be
reliably measured down to 0.1 mas/yr, and agree well with the line-of-sight
velocity dispersion profiles from the literature.
