Simulating dust grain-radiation coupling on a moving mesh

TL;DR

This paper introduces a novel model for simulating dust-radiation interactions within a moving mesh hydrodynamics code, enabling self-consistent calculations of dust effects on radiation fields and thermal emission in galaxy formation simulations.

Contribution

It presents a new hybrid scheme coupling dust particles with an unstructured moving mesh for radiation, validated through multiple test problems, and capable of modeling dust heating, emission, and non-equilibrium energy transfer.

Findings

Validated the dust-radiation coupling scheme with analytic tests.

Enabled self-consistent dust opacity and temperature calculations.

Compatible with multifrequency radiation transfer in galaxy simulations.

Abstract

We present a model for the interaction between dust and radiation fields in the radiation hydrodynamic code AREPO-RT, which solves the moment-based radiative transfer equations on an unstructured moving mesh. Dust is directly treated using live simulation particles, each of which represent a population of grains that are coupled to hydrodynamic motion through a drag force. We introduce methods to calculate radiation pressure on and photon absorption by dust grains. By including a direct treatment of dust, we are able to calculate dust opacities and update radiation fields self-consistently based on the local dust distribution. This hybrid scheme coupling dust particles to an unstructured mesh for radiation is validated using several test problems with known analytic solutions, including dust driven via spherically-symmetric flux from a constant luminosity source and photon absorption from radiation incident on a thin layer of dust. Our methods are compatible with the multifrequency scheme in AREPO-RT, which treats UV and optical photons as single-scattered and IR photons as multi-scattered. At IR wavelengths, we model heating of and thermal emission from dust. Dust and gas are not assumed to be in local thermodynamic equilibrium but transfer energy through collisional exchange. We estimate dust temperatures by balancing these dust-radiation and dust-gas energy exchange rates. This framework for coupling dust and radiation can be applied in future radiation hydrodynamic simulations of galaxy formation.