From the Top Down and Back Up Again: Star Cluster Structure from Hierarchical Star Formation

Understand

Young massive star clusters spanning $\sim 10^4 - 10^8 M_\odot$ in mass have been observed to have similar surface brightness profiles.

• Recent hydrodynamical simulations of star cluster formation have also produced star clusters with this structure.
• We argue analytically that this type of mass distribution arises naturally in the relaxation from a hierarchically-clustered distribution of stars into a monolithic star cluster through hierarchical merging.
• We show that arbitrary initial profiles will tend to converge to a universal profile under hierarchical merging, owing to phase-space mixing obeying certain conservation constraints.