Radiation-hydrodynamical simulations of massive star formation using Monte Carlo radiative transfer: I. Algorithms and numerical methods

TL;DR

This paper introduces advanced Monte Carlo-based numerical algorithms for simulating radiation pressure in massive star formation, incorporating microphysics, with improved efficiency and scalability for complex hydrodynamic environments.

Contribution

The paper presents novel Monte Carlo algorithms with photon packet splitting and parallelisation, enabling detailed radiation-hydrodynamics simulations of massive star formation.

Findings

Efficient photon packet splitting algorithm for optically thick regions

Parallelisation method achieves excellent scaling

Successful implementation of sink particles for protostar growth

Abstract

We present a set of new numerical methods that are relevant to calculating radiation pressure terms in hydrodynamics calculations, with a particular focus on massive star formation. The radiation force is determined from a Monte Carlo estimator and enables a complete treatment of the detailed microphysics, including polychromatic radiation and anisotropic scattering, in both the free-streaming and optically-thick limits. Since the new method is computationally demanding we have developed two new methods that speed up the algorithm. The first is a photon packet splitting algorithm that enables efficient treatment of the Monte Carlo process in very optically thick regions. The second is a parallelisation method that distributes the Monte Carlo workload over many instances of the hydrodynamic domain, resulting in excellent scaling of the radiation step. We also describe the implementation of a sink particle method that enables us to follow the accretion onto, and the growth of, the protostars. We detail the results of extensive testing and benchmarking of the new algorithms.