Hierarchical Formation in Young Solar Clusters
3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3 II: Hierarchical Star Formation Revealed by Spatial and Kinematic Substructures
We identify members of 65 open clusters in the solar neighborhood using the machine-learning algorithm stargo based on the data of the open cluster survey (edr3).We classify the substructures outside the tidal radius into four categories : filamentary(f1) and fractal (f2) for clusters myr, and halo (h) and tidal-tail (t) for clusters myr.We identify 29 hierarchical groups in four young regions (alessi 20, ic 348, lp 2373, and lp 2442) ; ten amongthese are new.The hierarchical groups form filament networks.Infalling-like flows (stellar motion along the filament) are found in hierarchical groups in the ic 348 region.The hierarchical groups in the lp 2442 region (lp 2442 gp 1-5) are spatially well-mixed but kinematically well-coherent.The kinematical substructures of f1-type clusters are elongated ; these resemble the disrupted cluster group x. kinematic tails aredistinct in t-type clusters, especially pleiades.The mean axis ratio, cluster mass and half-mass radius tend to increase with age.These correlations between structural parameters may imply two dynamical processes occurring in the hierarchical formation scenario in young stellar groups : (1) filament dissolution and (2) sub-group mergers.
