Journal article

No energy equipartition in globular clusters

Michele Trenti, Roeland van der Marel

Monthly Notices of the Royal Astronomical Society | OXFORD UNIV PRESS | Published : 2013


It is widely believed that globular clusters evolve overmany two-body relaxation times towards a state of energy equipartition, so that velocity dispersion scales with stellar mass as s σ α m η with = 0.5. We show here that this is incorrect, using a suite of direct N-body simulations with a variety of realistic initialmass functions and initial conditions. No simulated system ever reaches a state close to equipartition. Near the centre, the luminous main-sequence stars reach a maximum n ≈ 0.15 ± 0.03. At large times, all radial bins convergence on an asymptotic value n ≈ 0.08 ± 0.02. The development of this 'partial equipartition' is strikingly similar across our simulations, despite the..

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University of Melbourne Researchers


Awarded by NASA through STScI

Awarded by NASA

Awarded by Kavli Institute for Theoretical Physics through the National Science Foundation

Awarded by National Science Foundation through TeraGrid resources by the National Center for Supercomputing Applications

Funding Acknowledgements

The authors are grateful to Jay Anderson and Andrea Bellini for collaboration on related projects, and for providing observational drivers for this theoretical work. Andrea Bellini kindly provided his latest proper motion results on Omega Cen, which were compared to our simulations in Section 4. The authors thank Adriano Agnello for useful suggestions and discussions. Support of HST Theory proposals HST-AR-11284 and HST-AR-12156 was provided by NASA through grants from STScI, which is operated by AURA, Inc., under NASA contract NAS 5-26555. MT acknowledges support from the Kavli Institute for Theoretical Physics, through the National Science Foundation grant PHY05-51164. This research was supported in part by the National Science Foundation through TeraGrid resources provided by the National Center for Supercomputing Applications (grants TG-AST090045 and TG-AST090094). This project is part of the HSTPROMO collaboration,<SUP>8</SUP> a set of HST projects aimed at improving our dynamical understanding of stars, clusters and galaxies in the nearby Universe through measurement and interpretation of proper motions.