Rotation in young massive star clusters
  Hydrodynamical simulations of turbulent molecular clouds show that star
clusters form from the hierarchical merger of several sub-clumps. We run
smoothed-particle hydrodynamics simulations of turbulence-supported molecular
clouds with mass ranging from 1700 to 43000 Msun. We study the kinematic
evolution of the main cluster that forms in each cloud. We find that the parent
gas acquires significant rotation, because of large-scale torques during the
process of hierarchical assembly. The stellar component of the embedded star
cluster inherits the rotation signature from the parent gas. Only star clusters
with final mass < few X 100 Msun do not show any clear indication of rotation.
Our simulated star clusters have high ellipticity (~0.4-0.5 at t=4 Myr) and are
subvirial (Q_vir<~0.4). The signature of rotation is stronger than radial
motions due to subvirial collapse. Our results suggest that rotation is common
in embedded massive (>~1000 Msun) star clusters. This might provide a key
observational test for the hierarchical assembly scenario.
