Journal Article

A prescription and fast code for the long-term evolution of star clusters

Poul E. R. Alexander and Mark Gieles

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 422, issue 4, pages 3415-3432
Published in print June 2012 | ISSN: 0035-8711
Published online May 2012 | e-ISSN: 1365-2966 | DOI:
A prescription and fast code for the long-term evolution of star clusters

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We introduce the star cluster evolution code Evolve Me A Cluster of StarS (emacss), a simple yet physically motivated computational model that describes the evolution of some fundamental properties of star clusters in static tidal fields. We base our prescription upon the flow of energy within the cluster, which is a constant fraction of the total energy per half-mass relaxation time. According to Hénon’s predictions, this flow is independent of the precise mechanisms for energy production within the core, and therefore does not require a complete description of the many-body interactions therein. For a cluster of equal-mass stars, we use dynamical theory and analytic descriptions of escape mechanisms to construct a series of coupled differential equations expressing the evolution of cluster mass and radius. These equations are numerically solved using a fourth-order Runge–Kutta integration kernel, and the results benchmarked against a data base of direct N-body simulations. We use simulations containing a modest initial number of stars (1024 ≤N≤ 65 536) and point-mass tidal fields of various strengths. Our prescription is publicly available and reproduces the N-body results to within ∼10 per cent accuracy for the entire post-collapse evolution of star clusters.

Keywords: methods: numerical; globular clusters: general; galaxies: star clusters: general

Journal Article.  11435 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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