Simulating Star Clusters with the AMUSE Software Framework: I. Dependence of Cluster Lifetimes on Model Assumptions and Cluster Dissolution Modes

TL;DR

This study uses the AMUSE software to simulate star cluster evolution, revealing how initial conditions and dissolution modes influence cluster lifetimes, with findings on the impact of stochastic effects and identifying two distinct dissolution modes.

Contribution

It introduces the use of the AMUSE framework for star cluster simulations and analyzes the effects of initial conditions and dissolution modes on cluster lifetimes.

Findings

Random realization noise can alter cluster lifetime by up to 30%.

Two distinct dissolution modes identified: dynamical and relaxation dominated.

Boundary between dissolution modes depends on initial mass function and time scales.

Abstract

We perform a series of simulations of evolving star clusters using AMUSE (the Astrophysical Multipurpose Software Environment), a new community-based multi-physics simulation package, and compare our results to existing work. These simulations model a star cluster beginning with a King model distribution and a selection of power-law initial mass functions, and contain a tidal cut-off. They are evolved using collisional stellar dynamics and include mass loss due to stellar evolution. After determining that the differences between AMUSE results and prior publications are understood, we explored the variation in cluster lifetimes due to the random realization noise introduced by transforming a King model to specific initial conditions. This random realization noise can affect the lifetime of a simulated star cluster by up to 30%. Two modes of star cluster dissolution were identified: a mass evolution curve that contains a run-away cluster dissolution with a sudden loss of mass, and a dissolution mode that does not contain this feature. We refer to these dissolution modes as "dynamical" and "relaxation" dominated respectively. For Salpeter-like initial mass functions, we determined the boundary between these two modes in terms of the dynamical and relaxation time scales.