SCYON Abstract

Received on June 7 2012

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

Authors	Poul E.R. Alexander and Mark Gieles
Affiliation	Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA
Accepted by	Monthly Notices of the Royal Astronomical Society
Contact	pera@ast.cam.ac.uk
URL	http://arxiv.org/abs/1203.4744
Links

Abstract

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 Henon'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 thence use dynamical theory and analytic descriptions of escape mechanisms to construct a series of coupled differential equations expressing the time-evolution of cluster mass and radius. These equations are numerically solved using a 4th order Runge-Kutta integration kernel, and the results bench-marked against a database of direct N-body simulations. We use simulations containing a modest initial number of stars (1024 ≤ N ≤ 65536), and point-mass tidal fields of various strengths. Our prescription is publicly available, and reproduces the N-body results to within ~10% accuracy for the entire post-collapse evolution of star clusters.