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Rotation and Flattening of Globular Clusters

Published online by Cambridge University Press:  04 August 2017

S. Michael Fall
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 OHA England Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 USA
Carlos S. Frenk
Affiliation:
Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH England Institute for Theoretical Physics, University of California, Santa Barbara, California 93106 USA

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Pease and Shapley (1917) first remarked on the apparent flattening of several Galactic globular clusters, a view that has been confirmed by many subsequent studies. Tidal stresses, internal rotation, and velocity anisotropies can cause deviations from sphericity in stellar systems. In general, we might expect globular clusters to have some angular momentum at the time of formation and, if they collapsed from flattened initial conditions, to have anisotropic pressure support. Since the velocity distributions within the clusters can be altered by a variety of internal and external processes, their shapes are expected to evolve. In this article, we review the methods for measuring ellipticities and the results that have emerged from such studies. Our main purpose, however, is to discuss the processes that determine the shapes of globular clusters and the ways in which they change with time.

Type
May 30: Model System in the Point-Mass Approximation
Copyright
Copyright © Reidel 1985 

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