The early dynamical evolution of cool, clumpy star clusters
  Observations and theory both suggest that star clusters form sub-virial
(cool) with highly sub-structured distributions. We perform a large ensemble of
N-body simulations of moderate-sized (N=1000) cool, fractal clusters to
investigate their early dynamical evolution. We find that cool, clumpy clusters
dynamically mass segregate on a short timescale, that Trapezium-like massive
higher-order multiples are commonly formed, and that massive stars are often
ejected from clusters with velocities > 10 km/s (c.f. the average escape
velocity of 2.5 km/s). The properties of clusters also change rapidly on very
short timescales. Young clusters may also undergo core collapse events, in
which a dense core containing massive stars is hardened due to energy losses to
a halo of lower-mass stars. Such events can blow young clusters apart with no
need for gas expulsion. The warmer and less substructured a cluster is
initially, the less extreme its evolution.
