@misc{flitter_semi-analytical_2026,
	title = {Semi-analytical approach to {Ly}\$α\$ multiple-scattering in 21-cm signal simulations},
	url = {http://arxiv.org/abs/2601.14360},
	doi = {10.48550/arXiv.2601.14360},
	abstract = {A crucial physical quantity in determining the 21-cm signal during cosmic dawn is the inhomogeneous background of Lyα photons originating from the first galaxies. As these photons travel through the intergalactic medium (IGM), their scattering cross-section is often approximated as a delta function at resonance due to computational cost. That is, photons with emitted wavelengths between Lyα and Lyβ are assumed to travel in straight lines until they redshift into the Lyα resonance. However, due to the damping wing in the Lyα cross-section, this approximation fails as the frequency of the photon approaches the resonant frequency, resulting in multiple scatterings events that could be separated by non-negligible distances. These multiple scattering events effectively modify the intrinsic Lyα emissivity from galaxies. Some previous works studied this effect of Lyα multiple scattering by running computationally heavy radiative-transfer simulations. However, robustly interpreting the cosmic 21cm signal requires exploring a large parameter space of astrophysical uncertainties, motivating more computationally-efficient approaches. Here we incorporate Lyα multiple scatterings in the public, semi-numerical simulation 21cmFAST. To do so, we employ Monte Carlo simulations to study the trajectories of Lyα photons on different scales. We find that the distance distributions of Lyα photons with respect to the absorption point can be modeled as analytical functions that are governed by a single parameter. Upon implementing the distance distributions in 21cmFAST, we find that the multiple scattering effect is important (about 50\% difference in the 21-cm power spectrum) only at high redshifts before the spin temperature is fully coupled to the kinetic temperature. Furthermore, we find that Lyα multiple scattering does not enhance Lyα heating, and that the combined effect is negligible, especially under realistic X-ray heating scenarios.},
	language = {en},
	urldate = {2026-03-02},
	publisher = {arXiv},
	author = {Flitter, Jordan and Muñoz, Julian B. and Mesinger, Andrei},
	month = jan,
	year = {2026},
	note = {arXiv:2601.14360 [astro-ph]},
	keywords = {Astrophysics - Cosmology and Nongalactic Astrophysics},
}

{"_id":"8nr6Bi6dAxAaBfErR","bibbaseid":"flitter-muoz-mesinger-semianalyticalapproachtolymultiplescatteringin21cmsignalsimulations-2026","author_short":["Flitter, J.","Muñoz, J. B.","Mesinger, A."],"bibdata":{"bibtype":"misc","type":"misc","title":"Semi-analytical approach to Ly$α$ multiple-scattering in 21-cm signal simulations","url":"http://arxiv.org/abs/2601.14360","doi":"10.48550/arXiv.2601.14360","abstract":"A crucial physical quantity in determining the 21-cm signal during cosmic dawn is the inhomogeneous background of Lyα photons originating from the first galaxies. As these photons travel through the intergalactic medium (IGM), their scattering cross-section is often approximated as a delta function at resonance due to computational cost. That is, photons with emitted wavelengths between Lyα and Lyβ are assumed to travel in straight lines until they redshift into the Lyα resonance. However, due to the damping wing in the Lyα cross-section, this approximation fails as the frequency of the photon approaches the resonant frequency, resulting in multiple scatterings events that could be separated by non-negligible distances. These multiple scattering events effectively modify the intrinsic Lyα emissivity from galaxies. Some previous works studied this effect of Lyα multiple scattering by running computationally heavy radiative-transfer simulations. However, robustly interpreting the cosmic 21cm signal requires exploring a large parameter space of astrophysical uncertainties, motivating more computationally-efficient approaches. Here we incorporate Lyα multiple scatterings in the public, semi-numerical simulation 21cmFAST. To do so, we employ Monte Carlo simulations to study the trajectories of Lyα photons on different scales. We find that the distance distributions of Lyα photons with respect to the absorption point can be modeled as analytical functions that are governed by a single parameter. Upon implementing the distance distributions in 21cmFAST, we find that the multiple scattering effect is important (about 50% difference in the 21-cm power spectrum) only at high redshifts before the spin temperature is fully coupled to the kinetic temperature. Furthermore, we find that Lyα multiple scattering does not enhance Lyα heating, and that the combined effect is negligible, especially under realistic X-ray heating scenarios.","language":"en","urldate":"2026-03-02","publisher":"arXiv","author":[{"propositions":[],"lastnames":["Flitter"],"firstnames":["Jordan"],"suffixes":[]},{"propositions":[],"lastnames":["Muñoz"],"firstnames":["Julian","B."],"suffixes":[]},{"propositions":[],"lastnames":["Mesinger"],"firstnames":["Andrei"],"suffixes":[]}],"month":"January","year":"2026","note":"arXiv:2601.14360 [astro-ph]","keywords":"Astrophysics - Cosmology and Nongalactic Astrophysics","bibtex":"@misc{flitter_semi-analytical_2026,\n\ttitle = {Semi-analytical approach to {Ly}\\$α\\$ multiple-scattering in 21-cm signal simulations},\n\turl = {http://arxiv.org/abs/2601.14360},\n\tdoi = {10.48550/arXiv.2601.14360},\n\tabstract = {A crucial physical quantity in determining the 21-cm signal during cosmic dawn is the inhomogeneous background of Lyα photons originating from the first galaxies. As these photons travel through the intergalactic medium (IGM), their scattering cross-section is often approximated as a delta function at resonance due to computational cost. That is, photons with emitted wavelengths between Lyα and Lyβ are assumed to travel in straight lines until they redshift into the Lyα resonance. However, due to the damping wing in the Lyα cross-section, this approximation fails as the frequency of the photon approaches the resonant frequency, resulting in multiple scatterings events that could be separated by non-negligible distances. These multiple scattering events effectively modify the intrinsic Lyα emissivity from galaxies. Some previous works studied this effect of Lyα multiple scattering by running computationally heavy radiative-transfer simulations. However, robustly interpreting the cosmic 21cm signal requires exploring a large parameter space of astrophysical uncertainties, motivating more computationally-efficient approaches. Here we incorporate Lyα multiple scatterings in the public, semi-numerical simulation 21cmFAST. To do so, we employ Monte Carlo simulations to study the trajectories of Lyα photons on different scales. We find that the distance distributions of Lyα photons with respect to the absorption point can be modeled as analytical functions that are governed by a single parameter. Upon implementing the distance distributions in 21cmFAST, we find that the multiple scattering effect is important (about 50\\% difference in the 21-cm power spectrum) only at high redshifts before the spin temperature is fully coupled to the kinetic temperature. Furthermore, we find that Lyα multiple scattering does not enhance Lyα heating, and that the combined effect is negligible, especially under realistic X-ray heating scenarios.},\n\tlanguage = {en},\n\turldate = {2026-03-02},\n\tpublisher = {arXiv},\n\tauthor = {Flitter, Jordan and Muñoz, Julian B. and Mesinger, Andrei},\n\tmonth = jan,\n\tyear = {2026},\n\tnote = {arXiv:2601.14360 [astro-ph]},\n\tkeywords = {Astrophysics - Cosmology and Nongalactic Astrophysics},\n}\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n","author_short":["Flitter, J.","Muñoz, J. B.","Mesinger, A."],"key":"flitter_semi-analytical_2026","id":"flitter_semi-analytical_2026","bibbaseid":"flitter-muoz-mesinger-semianalyticalapproachtolymultiplescatteringin21cmsignalsimulations-2026","role":"author","urls":{"Paper":"http://arxiv.org/abs/2601.14360"},"keyword":["Astrophysics - Cosmology and Nongalactic Astrophysics"],"metadata":{"authorlinks":{}}},"bibtype":"misc","biburl":"https://bibbase.org/zotero-group/pratikmhatre/5933976","dataSources":["yJr5AAtJ5Sz3Q4WT4"],"keywords":["astrophysics - cosmology and nongalactic astrophysics"],"search_terms":["semi","analytical","approach","multiple","scattering","signal","simulations","flitter","muñoz","mesinger"],"title":"Semi-analytical approach to Ly$α$ multiple-scattering in 21-cm signal simulations","year":2026}