MAGI: many-component galaxy initialiser

TL;DR

MAGI is a fast, flexible, and open-source initial-condition generator for galactic N-body simulations that produces stable, multi-component galaxy models with various density profiles, supporting large particle numbers efficiently.

Contribution

The paper introduces MAGI, a novel distribution-function-based initial-condition generator for multi-component galaxies, supporting custom models and multiple discs, with demonstrated stability and rapid execution.

Findings

Models remain stable for over 1 Gyr.

Generation times are 8.5 and 221.7 seconds for large models.

Supports various density models and multiple discs.

Abstract

Providing initial conditions is an essential procedure for numerical simulations of galaxies. The initial conditions for idealised individual galaxies in $N$-body simulations should resemble observed galaxies and be dynamically stable for time scales much longer than their characteristic dynamical times. However, generating a galaxy model ab initio as a system in dynamical equilibrium is a difficult task, since a galaxy contains several components, including a bulge, disc, and halo. Moreover, it is desirable that the initial-condition generator be fast and easy to use. We have now developed an initial-condition generator for galactic $N$-body simulations that satisfies these requirements. The developed generator adopts a distribution-function-based method, and it supports various kinds of density models, including custom-tabulated inputs and the presence of more than one disc. We tested the dynamical stability of systems generated by our code, representing early- and late-type galaxies, with $N=$~2,097,152 and 8,388,608 particles, respectively, and we found that the model galaxies maintain their initial distributions for at least 1~Gyr. The execution times required to generate the two models were $8.5$ and $221.7$ seconds, respectively, which is negligible compared to typical execution times for $N$-body simulations. The code is provided as open-source software and is publicly and freely available at \url{https://bitbucket.org/ymiki/magi}.