18 février 2020A renewed look at Globular Clusters in the era of precision astrometry

Paolo Bianchini (ObAS)

The traditional picture of Globular Clusters (GCs) as simple stellar systems is being radically revolutionized by the synergistic efforts of theoretical advances and precision astrometry led by Gaia DR2. We now know that GCs present rich kinematic features, such as the presence of internal rotation and complex stellar populations. Both these elements strongly puzzle our understanding of GC formation in the early universe. In this talk I will show that the detailed study of GCs internal kinematics can provide the ideal “fossil record” to unveil their formation and their subsequent dynamical evolution in the Milky Way. First, I will show how to exploit subtle kinematic effects due to dynamical relaxation, such as energy equipartition, to trace the state and the current properties of GCs, including the presence of dark remnants. Then I will illustrate my effort in exploiting Gaia DR2 to measure these rich kinematic features, in parallel with a careful assessment of data systematics, and I will report the detection of significant amount of angular momentum in a sample of ~50 GCs. Finally, I will outline the implications of these findings for the formation mechanism of proto-GCs, their dissolution in the Milky Way stellar halo and their possible connection with Nuclear Star Clusters.