Binaries and the dynamical mass of star clusters

M. B.N. Kouwenhoven, R. De Grijs

Research output: Contribution to journalArticlepeer-review

Abstract

The total mass of a distant star cluster is often derived from the virial theorem, using line-of-sight velocity dispersion measurements and half-light radii, under the implicit assumption that all stars are single (although it is known that most stars form part of binary systems). The components of binary stars exhibit orbital motion, which increases the measured velocity dispersion, resulting in a dynamical mass overestimation. In these proceedings we quantify the effect of neglecting the binary population on the derivation of the dynamical mass of a star cluster. We find that the presence of binaries plays an important role for clusters with total mass Mcl 105 M; the dynamical mass can be significantly overestimated (by a factor of two or more). For the more massive clusters, with Mcl 105 M, binaries do not affect the dynamical mass estimation significantly, provided that the cluster is significantly compact (half-mass radius qslant 5 pc).

Original languageEnglish
Pages (from-to)269-270
Number of pages2
JournalProceedings of the International Astronomical Union
Volume3
Issue numberS246
DOIs
Publication statusPublished - Sept 2007
Externally publishedYes

Keywords

  • Binaries: general
  • Methods: numerical
  • Star clusters

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