Astron. Astrophys. 330, 480-491 (1998)

The initial distribution and evolution of globular cluster systems

H. Baumgardt

Astronomisches Rechen-Institut Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg, Germany (holger@relay.ari.uni-heidelberg.de)

Received 17 April 1997 / Accepted 13 August 1997

Abstract

This work considers the evolution of globular cluster systems in galaxies. Here globular cluster systems start with power-law mass functions with slopes around 2.0, similar to what has been observed for the young luminous clusters seen in merging and interacting galaxies. We then follow the orbits of the clusters through their parent galaxy, allowing various destruction mechanisms to dissolve them. In comparing the surviving distribution to the observed one, we show that our model can reproduce several aspects of present day globular cluster systems.

This method is employed to the globular clusters of the Milky Way and M87. In the case of the Milky Way we obtain luminosity distributions, which depend on the galactocentric distance in a way similar to what is observed. We also observe a change in the velocity distribution of the globular cluster system, which predicts a different kinematical state of the surviving halo clusters compared to the halo stars. The final luminosity function of the globular cluster system in M87 can differ from the one found for the Milky Way clusters, which casts doubt on the use of globular cluster luminosity functions to measure distances. We also discuss some implications of our results for the dynamical history of M87.

Key words: Galaxy: globular clusters: general galaxies: star clusters galaxies: individual: M87

Send offprint requests to: H. Baumgardt

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Contents

• 1. Introduction
• 2. The destruction processes
  • 2.1. Internal dissolution and the galactic tidal field
    • 2.1.1. Isolated clusters
    • 2.1.2. The presence of a tidal field
  • 2.2. Dynamical friction
  • 2.3. Disk shocking
• 3. Initial condition and related problems
  • 3.1. The distribution of cluster masses
  • 3.2. The initial distribution of half-mass radii
  • 3.3. The model for the Milky Way
  • 3.4. The distribution of the clusters in the Milky Way
  • 3.5. The initial velocity distribution
  • 3.6. The age of the cluster system
  • 3.7. The model for M87
• 4. Results
  • 4.1. Results for the Milky Way globular cluster system
  • 4.2. Results for M87
• 5. Summary
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
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