Description
Recent surveys have provided a much more complete census of nearby star-forming regions and their populations of young stars. Notably, the Gaia mission has revealed the 3D structures of these regions and the kinematics of their members. On spatial scales ranging from molecular cloud clumps to giant multi-kpc filaments, the processes of molecular cloud assembly, turbulent collapse, and dispersal initialise the dynamical states of young stellar clusters and associations. On small scales, velocity dispersions in clouds are reflected in the velocity dispersions of the young stars they form (e.g., the Trifid Nebula), and the turbulent motions in clouds are reflected in the subclustering of young stars in position-velocity space (e.g., the North America/Pelican Nebulae). On intermediate scales, the disruption of molecular clouds by stellar radiation and winds likely drives the expansion and dispersal of young clusters and associations in many star-forming regions due to both the disruptive effects of mass loss and star formation in expanding cloud shells (e.g., the Cygnus X region). Finally, on multi-kpc scales, the assembly of molecular gas into giant filaments imprints itself on the Galactic orbits of young clusters and associations. Together, these multi-scale processes help explain why most massive star-forming regions do not produce bound open clusters and why stellar associations exhibit complex internal kinematics.
