Rotating globular clusters. III. Evolutionary survey.
Abstract
We describe a simple model which allows us to investigate the effects of rotation on the evolution of globular clusters and of their flattening. The model relies on a generalization to rotating clusters of sequences of quasi-equilibrium models known as King sequences, which are able to follow the evolution of globular clusters prior to core collapse. Our model includes in a simplified way the effects of internal relaxation, tidal heating by passage through the Galactic disk, and stellar evolution. We investigate a broad range of initial conditions in the cluster mass, Galactocentric distance, initial mass function power-law index, initial concentration, and initial rotation energy. We also report the results of a similar study of the Large Magellanic Cloud clusters. The major findings of this investigation are the following: i) the combined effects of rotation, tidal shocking and stellar evolution is to reduce the domain of survival of rotating clusters to higher concentrations with respect to nonrotating ones; ii) rotating clusters reach core collapse at lower concentrations than their nonrotating counterparts; iii) the three modelled processes are likely to be responsible for the luminosity/flattening and relaxation timescale/flattening correlations reported in the literature; iv) the larger flattening of the Magellanic globular clusters is mostly the result of their large spread in age, as reported by Frenk and Fall (1982MNRAS.199..565F), and, to a lesser extent, of the smaller efficiency of the evolution in the Magellanic Cloud tidal environment with respect to the Galaxy, assuming similar initial conditions.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- March 1997
- Bibcode:
- 1997A&A...319..839L
- Keywords:
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- CELESTIAL MECHANICS;
- STELLAR DYNAMICS;
- GLOBULAR CLUSTERS;
- GALAXIES: STAR CLUSTERS;
- MAGELLANIC CLOUDS