Magritte，一个现代三维辐射转移软件库：I。非LTE原子和分子线模型
Magritte, a modern software library for 3D radiative transfer: I. Non-LTE atomic and molecular line modelling
摘要：
辐射转移是几乎所有天体物理学和宇宙学模拟的关键组成部分。我们提出了Magritte：一个现代的开源软件库的三维辐射转移。它使用确定性射线跟踪器和形式求解器，即通过跟踪穿过模型的射线并沿着源自每个点的固定射线集以其二阶形式求解辐射转移方程来计算辐射场。Magritte可以处理结构化和非结构化输入网格，以及光滑粒子流体动力学（SPH）粒子数据。在这第一篇论文中，我们描述了数值实现，半解析测试和交叉代码基准的非LTE线辐射转移模块的Magritte。该模块使用辐射转移求解器，使用加速Lambda迭代（ALI）方案自洽地确定原子和分子的量子化能级的布居。我们比较了Magritte与已建立的辐射转移求解器Ratran（1D）和Lime（3D）的van Zadelhoff基准，并提出了一个简单的开普勒圆盘模型的第一个应用程序。与Lime相比，Magritte方法的计算结果更精确，特别是在高光学深度下，而且计算速度更快。
英文摘要：
Radiative transfer is a key component in almost all astrophysical and cosmological simulations. We present Magritte: a modern open-source software library for 3D radiative transfer. It uses a deterministic ray-tracer and formal solver, i.e. it computes the radiation field by tracing rays through the model and solving the radiative transfer equation in its second-order form along a fixed set of rays originating from each point. Magritte can handle structured and unstructured input meshes, as well as smoothed-particle hydrodynamics (SPH) particle data. In this first paper, we describe the numerical implementation, semi-analytic tests and cross-code benchmarks for the non-LTE line radiative transfer module of Magritte. This module uses the radiative transfer solver to self-consistently determine the populations of the quantised energy levels of atoms and molecules using an accelerated Lambda iteration (ALI) scheme. We compare Magritte with the established radiative transfer solvers Ratran (1D) and Lime (3D) on the van Zadelhoff benchmark and present a first application to a simple Keplerian disc model. Comparing with Lime, we conclude that Magritte produces more accurate and more precise results, especially at high optical depth, and that it is faster.
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