Journal Article

The early dynamical evolution of cool, clumpy star clusters

Richard J. Allison, Simon P. Goodwin, Richard J. Parker, Simon F. Portegies Zwart and Richard de Grijs

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 2, pages 1098-1107
Published in print September 2010 | ISSN: 0035-8711
Published online September 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16939.x
The early dynamical evolution of cool, clumpy star clusters

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Observations and theory both suggest that star clusters form subvirial (cool) with highly substructured 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 time-scale, that Trapezium-like massive higher order multiples are commonly formed, and that massive stars are often ejected from clusters with velocities >10 km s−1 (cf. the average escape velocity of 2.5 km s−1). The properties of clusters also change rapidly on very short time-scales. 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.

Keywords: stars: formation; stars: kinematics and dynamics

Journal Article.  6991 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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