Chronostar. II. Kinematic age and substructure of the Scorpius-Centaurus
  OB2 association
  The nearest region of massive star formation - the Scorpius-Centaurus OB2
association (Sco-Cen) - is a local laboratory ideally suited to the study of a
wide range of astrophysical phenomena. Precision astrometry from the Gaia
mission has expanded the census of this region by an order of magnitude.
However, Sco-Cen's vastness and complex substructure make kinematic analysis of
its traditional three regions, Upper Scorpius, Upper Centaurus-Lupus and Lower
Centaurus-Crux, challenging. Here we use Chronostar, a Bayesian tool for
kinematic age determination, to carry out a new kinematic decomposition of
Sco-Cen using full 6-dimensional kinematic data. Our model identifies 8
kinematically distinct components consisting of 8,185 stars distributed in
dense and diffuse groups, each with an independently-fit kinematic age; we
verify that these kinematic estimates are consistent with isochronal ages. Both
Upper Centaurus-Lupus and Lower Centaurus-Crux are split into two parts. The
kinematic age of the component that includes PDS 70, one of the most well
studied systems currently forming planets, is 15$\pm$3 Myr.
