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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2511.20580 |
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| _version_ | 1866912910238810112 |
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| author | Stace, Ethan Smith, Aaron Lorinc, Kevin Nebrin, Olof |
| author_facet | Stace, Ethan Smith, Aaron Lorinc, Kevin Nebrin, Olof |
| contents | Resonance lines encode rich information about astrophysical sources and their environments, yet fully analytic treatments of multi-line radiative transfer remain almost entirely unexplored. We present exact, closed-form solutions for steady-state resonant-line radiative transfer in "V-shaped" atomic networks, where a single ground state couples to multiple transitions. Starting from the full angle-dependent transfer equation, we generalize absorption and emission coefficients to an arbitrary number of lines, derive a modified Fokker-Planck expansion of the frequency-redistribution COLT Monte Carlo radiative transfer code and find excellent agreement with the analytic predictions across a wide range of line separations, optical depths, and damping parameters, establishing our solutions as stringent validation benchmarks. For concrete applications related to the Lyman-alpha transition of neutral hydrogen, we examine how fine-structure splitting and deuterium injection modify the emergent spectra, internal radiation field, and radiative force multiplier. We show that these effects leave previous conclusions about Lyman-alpha feedback in the early universe essentially unchanged. Even when direct observational diagnostics are subtle, our framework provides novel analytic and numerical insights into coupled resonance-line transport and facilitates progress in general modeling of multi-line radiative transfer in diverse astrophysical settings. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_20580 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Multi-Resonant-Line Radiative Transfer: Lyman-Alpha Fine Structure and Deuterium Coupling Stace, Ethan Smith, Aaron Lorinc, Kevin Nebrin, Olof Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics Resonance lines encode rich information about astrophysical sources and their environments, yet fully analytic treatments of multi-line radiative transfer remain almost entirely unexplored. We present exact, closed-form solutions for steady-state resonant-line radiative transfer in "V-shaped" atomic networks, where a single ground state couples to multiple transitions. Starting from the full angle-dependent transfer equation, we generalize absorption and emission coefficients to an arbitrary number of lines, derive a modified Fokker-Planck expansion of the frequency-redistribution COLT Monte Carlo radiative transfer code and find excellent agreement with the analytic predictions across a wide range of line separations, optical depths, and damping parameters, establishing our solutions as stringent validation benchmarks. For concrete applications related to the Lyman-alpha transition of neutral hydrogen, we examine how fine-structure splitting and deuterium injection modify the emergent spectra, internal radiation field, and radiative force multiplier. We show that these effects leave previous conclusions about Lyman-alpha feedback in the early universe essentially unchanged. Even when direct observational diagnostics are subtle, our framework provides novel analytic and numerical insights into coupled resonance-line transport and facilitates progress in general modeling of multi-line radiative transfer in diverse astrophysical settings. |
| title | Multi-Resonant-Line Radiative Transfer: Lyman-Alpha Fine Structure and Deuterium Coupling |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2511.20580 |