The Effect of Stellar Metallicity on the Sizes of Star Clusters

Abstract

Observations indicate blue globular clusters have half-light radii systematically larger than those of red globular clusters. In this paper, we test whether the different metallicity-dependent stellar evolution timescales and mass-loss rates within the clusters can impact their early dynamical evolution. By means of N-body simulations including stellar evolution recipes we simulate the early evolution of small centrally concentrated clusters with and without primordial mass segregation. Our simulations include accurate metallicity-dependent mass loss from massive stars. We find blue clusters to be larger than red clusters regardless of whether the clusters have been primordially mass segregated. In addition, the size difference is found to be larger and consistent with observations for initial models with a low central concentration. These results indicate that the systematic size difference found between red and blue clusters can, at least in part, be attributed to the dynamical effects of differing stellar evolution histories, driven by metallicity.

8 pages, 5 figures, accepted by MNRAS

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• Globular Cluster Scale Sizes in Giant Galaxies: The Case of M87 and the Role of Orbital Anisotropy and Tidal Filling
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• Globular Cluster Scale Sizes in Giant Galaxies: Orbital Anisotropy and Tidally Under-filling Clusters in M87, NGC 1399, and NGC 5128
• The X-ray Binary-Star Cluster Connection in Late-Type Galaxies
• Searching for globular clusters in the inner halo of the Circinus galaxy