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Black Holes and Core Expansion in Massive Star Clusters

Published online by Cambridge University Press:  01 September 2007

A. D. Mackey ,
M. I. Wilkinson ,
M. B. Davies  and
G. F. Gilmore
A. D. Mackey
Affiliation:
Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK; email: dmy@roe.ac.uk
M. I. Wilkinson
Affiliation:
Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
M. B. Davies
Affiliation:
Lund Observatory, Box 43, SE-221 00 Lund, Sweden
G. F. Gilmore
Affiliation:
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
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Abstract

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Massive star clusters in the Magellanic Clouds are observed to follow a striking trend in size with age – older clusters exhibit a much greater spread in core radius than do younger clusters, which are generally compact. We present results from realistic N-body modelling of massive star clusters, aimed at investigating a dynamical origin for the radius-age trend. We find that stellar-mass black holes, formed as remnants of the most massive stars in a cluster, can constitute a dynamically important population. If retained, these objects rapidly form a dense core where interactions are common, resulting in the scattering of black holes into the cluster halo, and the ejection of black holes from the cluster. These processes heat the stellar component, resulting in prolonged core expansion of a magnitude matching the observations. Core expansion at early times does not result from the action of black holes, but can be reproduced by the effects of rapid mass-loss due to stellar evolution in a primordially mass segregated cluster.

Keywords

Stellar dynamicsN-body simulationsgalaxies: star clustersMagellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 176 - 180
Copyright
Copyright © International Astronomical Union 2008

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