Modeling the kinematics of globular cluster systems
  Globular clusters (GCs) are old massive star clusters that serve as "fossils"
of galaxy formation. The advent of Gaia observatory has enabled kinematics
studies of the Galactic GCs with great detail and revolutionized our
understanding of the connections between GC properties and galaxy assembly.
However, lack of kinematic measurements of extragalactic GCs limits the sample
size of GC systems that we can fully study observationally. In this work, we
present a model for GC formation and evolution, which includes positional and
kinematic information of individual GCs by assigning them to particles in the
Illustris TNG50-1 simulation based on the age and location. The model
predictions are consistent with many observed properties of GC systems,
including the distributions of position, systemic velocity, velocity
dispersion, anisotropy parameter, orbital actions, and metallicities. We also
analyze the properties of GCs from different origins. In the outer galaxy,
ex-situ clusters are more dominant than the clusters formed in-situ. This leads
to the GC metallicities decreasing outwards due to the increasing abundance of
accreted, metal-poor clusters. We also find the ex-situ GCs to have greater
velocity dispersions and orbital actions, in agreement with their accretion
origin.
