Kratos-linerad: GPU-accelerated Monte Carlo radiative transfer of lines with efficient imaging

Lile Wang

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arXiv · 2608.09340

Kratos-linerad: GPU-accelerated Monte Carlo radiative transfer of lines with efficient imaging

Lile Wang

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Abstract

Spectral lines encode the velocity, the temperature, and the chemical structure of astrophysical gas; interpreting them requires radiative transfer that is accurate at high optical depth, consistent with the local excitation, and efficient enough to synthesize velocity-resolved images. We present Kratos-linerad, a GPU-accelerated Monte Carlo radiative transfer code for spectral lines. The level populations can be iterated to statistical equilibrium together with the escaping photon distribution, treating angle-dependent partial frequency redistribution through constant-memory sampling tables. The code adopts the two-step imaging scheme to line transfer, in which a Monte Carlo pass samples a velocity-resolved scattering emissivity, and a deterministic ray-tracing pass synthesizes channel maps decoupled from the scattering geometry. Validation reproduces the analytic scaling of escaped spectra and the imaging double-peak profiles. GPU parallelism enables both stages sufficiently fast for routine application to astrophysically realistic models.

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Lile Wang. 2026-08-10. Kratos-linerad: GPU-accelerated Monte Carlo radiative transfer of lines with efficient imaging. https://arxiv.org/abs/2608.09340

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