RAYTHEIA: A high-performance ray-tracing algorithm for three-dimensional direction-dependent equations in astronomical simulations

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ID: 313602
2026
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Ranked #401 of 913 articles by views in monthly notices of the royal astronomical society

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Abstract
Abstract We present raytheia, a high-performance reverse ray-tracing algorithm designed to efficiently solve three-dimensional direction-dependent equations in astronomical simulations. The algorithm uses a dual-grid framework in which the native simulation mesh -serving as the source grid for ray emission- and an adaptive mesh refinement (AMR) Cartesian contribution grid are constructed for efficient ray-walking and contribution accumulation. The core of the algorithm integrates a leaf-only linear-octree data structure to reduce memory overhead, the digital differential analyzer (DDA) traversal method to efficiently determine the ray-walking path, Morton Code indexing to fast leaf cell lookup during traversal, and the slab method to analytically compute the path length. Furthermore, raytheia employs a hybrid (MPI/OpenMP) distributed parallel framework with a chunk-to-chunk communication strategy, achieving exceptional, near-ideal linear speed-up ratio and delivering high-end performance. We integrate raytheia with the 3d-pdr code to solve the complex chemistry and radiation transfer in photodissociation regions (PDRs). This allowed the modelling of three-dimensional PDR chemistry in a turbulent, star-forming cloud at an unprecedented resolution of 5123 grid cells. The algorithm demonstrates accuracy and convergence even at low angular resolutions. We further showcase the capabilities of raytheia by producing high-resolution synthetic emission maps of key diagnostic lines of a star-forming region capturing physical effects such as [Oi] 63μm self-absorption, measuring the [Ci]-bright but CO-dark molecular gas, and deriving a CO-to-H2 conversion factor in agreement with observations.
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openalex_W7161177132 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors Zhengping Zhu, Thomas G. Bisbas, Xuefei Tang, Brandt A L Gaches, Tianwei Zhang, Huaxi Chen
Journal monthly notices of the royal astronomical society
Year 2026
DOI
10.1093/mnras/stag906
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Keywords Keywords not found

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