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Dynamical Evolution of Outer-Halo Globular Clusters

Published online by Cambridge University Press:  31 March 2017

Andreas H. W. Küpper ,
Akram H. Zonoozi ,
Hosein Haghi ,
Nora Lützgendorf ,
Steffen Mieske ,
Matthias Frank ,
Holger Baumgardt  and
Pavel Kroupa
Andreas H. W. Küpper
Affiliation:
Department of Astronomy, Columbia University, New York, NY 10027, USA email: akuepper@astro.columbia.edu
Akram H. Zonoozi
Affiliation:
Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
Hosein Haghi
Affiliation:
Department of Physics, Institute for Advanced Studies in Basic Sciences, Zanjan, Iran
Nora Lützgendorf
Affiliation:
ESA, Space Science Department, Keplerlaan 1, NL-2200 AG Noordwijk, The Netherlands
Steffen Mieske
Affiliation:
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
Matthias Frank
Affiliation:
Landessternwarte, Universität Heidelberg, Königsstuhl 12, 69117 Heidelberg, Germany
Holger Baumgardt
Affiliation:
University of Queensland, School of Mathematics and Physics, Brisbane, QLD 4072, Australia
Pavel Kroupa
Affiliation:
HISKP, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany
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Abstract

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Outer-halo globular clusters show large half-light radii and flat stellar mass functions, depleted in low-mass stars. Using N-body simulations of globular clusters on eccentric orbits within a Milky Way-like potential, we show how a cluster’s half-mass radius and its mass function develop over time. The slope of the central mass function flattens proportionally to the amount of mass a cluster has lost, and the half-mass radius grows to a size proportional to the average strength of the tidal field. The main driver of these processes is mass segregation of dark remnants. We conclude that the extended, depleted clusters observed in the Milky Way must have had small half-mass radii in the past, and that they expanded due to the weak tidal field they spend most of their lifetime in. Moreover, their mass functions must have been steeper in the past but flattened significantly as a cause of mass segregation and tidal mass loss.

Keywords

methods: n-body simulationsglobular clusters: generalGalaxy: halo
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S316: Formation, evolution, and survival of massive star clusters , August 2015 , pp. 257 - 258
Copyright
Copyright © International Astronomical Union 2017 

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