Analytical model for scattered Lyα emission in the post-reionization intergalactic medium
Lyα intensity mapping is emerging as a new probe of faint galaxies consisting the cosmic web that elude traditional surveys. - However, the resonant nature of Lyα radiative transfer complicates the interpretation of observed data. In this study, we develop a fast and accurate analytical prescription...
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| Main Authors: | , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
11 November 2025
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2025, Volume: 544, Issue: 4, Pages: 4246-4255 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/staf1971 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1093/mnras/staf1971 Verlag, kostenfrei, Volltext: https://academic.oup.com/mnras/article/544/4/4246/8320521?login=true 
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| Author Notes: | Hyunbae Park, Hyunmi Song, Chris Byrohl, Aaron Smith, Hidenobu Yajima, Zarija Lukić |
| Summary: | Lyα intensity mapping is emerging as a new probe of faint galaxies consisting the cosmic web that elude traditional surveys. - However, the resonant nature of Lyα radiative transfer complicates the interpretation of observed data. In this study, we develop a fast and accurate analytical prescription for computing the Lyα intensity field on Mpc scales in the post-reionization Universe. Motivated by insights from Monte Carlo radiative transfer (MCRT) experiments, we exploit the fact that in a highly ionized intergalactic medium (IGM) with negligible damping-wing opacity, cosmological redshifting quickly drives Lyα photons out of resonance, terminating the scattering process and simplifying their large-scale behaviour. Photons emitted blueward of the Lyα line centre tend to scatter on a thin, nearly spherical surface of last scattering, with a radius determined by the redshifting distance to resonance. Based on this behaviour, we derive closed-form expressions for the scattered emissivity and projected surface brightness that depend only on the source spectrum, the H i density, and the peculiar velocity field. When applied to a source in a realistically simulated IGM at z = 3, our model shows mild discrepancies with MCRT results within a physical Mpc of the host halo, where strong gravitational infall redistributes the scattered photons, but achieves better than 5 per cent accuracy beyond that distance in angle-averaged radial surface brightness profile. Our prescription offers a computationally efficient alternative to MCRT for forward-modelling Lyα intensity maps from cosmological simulations, enabling the inference of underlying cosmological and astrophysical parameters from future observations. |
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| Item Description: | Gesehen am 09.03.2026 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/staf1971 |