A hybrid SPH/N-body method for star cluster simulations

TL;DR

This paper introduces a conservative hybrid SPH/N-body simulation method for modeling young star clusters with gas, bridging detailed hydrodynamics and pure N-body approaches, and demonstrates its effectiveness through tests.

Contribution

A new Lagrangian-based hybrid SPH/N-body scheme implemented in SEREN that conserves physical quantities and is suitable for star cluster simulations with gas.

Findings

Successfully implemented in SEREN code

Demonstrated conservation properties and fidelity

Established resolution criteria for simulations

Abstract

We present a new hybrid Smoothed Particle Hydrodynamics (SPH)/N-body method for modelling the collisional stellar dynamics of young clusters in a live gas background. By deriving the equations of motion from Lagrangian mechanics we obtain a formally conservative combined SPH/N-body scheme. The SPH gas particles are integrated with a 2nd order Leapfrog, and the stars with a 4th order Hermite scheme. Our new approach is intended to bridge the divide between the detailed, but expensive, full hydrodynamical simulations of star formation, and pure N-body simulations of gas-free star clusters. We have implemented this hybrid approach in the SPH code SEREN (Hubber et al. 2011) and perform a series of simple tests to demonstrate the fidelity of the algorithm and its conservation properties. We investigate and present resolution criteria to adequately resolve the density field and to prevent strong numerical scattering effects. Future developments will include a more sophisticated treatment of binaries.