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A Dynamical Origin for Early Mass Segregation in Young Star Clusters

Published online by Cambridge University Press:  01 September 2007

Steve McMillan
Affiliation:
Department of Physics, Drexel University, Philadelphia, PA 19104, USA email: steve@physics.drexel.edu, vesperin@physics.drexel.edu
Enrico Vesperini
Affiliation:
Department of Physics, Drexel University, Philadelphia, PA 19104, USA email: steve@physics.drexel.edu, vesperin@physics.drexel.edu
Simon Portegies Zwart
Affiliation:
Astronomical Institute ‘Anton Pannekoek’ and Section Computational Science, University of Amsterdam, Kruislaan 403, 1098SJ Amsterdam, the Netherlands email: spz@science.uva.nl
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Abstract

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Some young star clusters show a degree of mass segregation that is inconsistent with the effects of standard two-body relaxation from an initially unsegregated system without substructure, in virial equilibrium, and it is unclear whether current cluster formation models can account for this degree of initial segregation in clusters of significant mass. We show that mergers of small clumps that are either initially mass segregated, or in which mass segregation can be produced by two-body relaxation before they merge, generically lead to larger systems which inherit the progenitor clumps' segregation. We conclude that clusters formed in this way are naturally mass segregated, accounting for the anomalous observations and suggesting that this process of prompt mass segregation due to initial clumping should be taken into account in models of cluster formation and dynamics.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008

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