Magritte, a modern software library for spectral line radiative transfer

TL;DR

Magritte is an open-source software library designed for spectral line radiative transfer, featuring improved algorithms and interfaces to enhance modeling efficiency and accuracy in astrophysical research.

Contribution

This paper introduces the first stable release of Magritte, with novel improvements like re-meshing, Ng-acceleration variation, and a semi-analytic optical depth approximation.

Findings

Enhanced re-meshing algorithm for spatial discretisation

Implementation of a variation of Ng-acceleration for faster convergence

Semi-analytic approximation for line optical depths with velocity gradients

Abstract

Spectral line observations are an indispensable tool to remotely probe the physical and chemical conditions throughout the universe. Modelling their behaviour is a computational challenge that requires dedicated software. In this paper, we present the first long-term stable release of Magritte, an open-source software library for line radiative transfer. First, we establish its necessity with two applications. Then, we introduce the overall design strategy and the application/programmer interface (API). Finally, we present three key improvements over previous versions: (1) an improved re-meshing algorithm to efficiently coarsen the spatial discretisation of a model; (2) a variation on Ng-acceleration, a popular acceleration-of-convergence method for non-LTE line transfer; and, (3) a semi-analytic approximation for line optical depths in the presence of large velocity gradients.