Scattering of Lyα Photons through the Reionizing Intergalactic Medium: I. Spectral Energy Distribution - Archive ouverte HAL Access content directly
Journal Articles The Astrophysical Journal Year : 2022

Scattering of Lyα Photons through the Reionizing Intergalactic Medium: I. Spectral Energy Distribution

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Hyunbae Park
  • Function : Author
Hyo Jeong Kim
  • Function : Author
Kyungjin Ahn
  • Function : Author
Hyunmi Song
  • Function : Author
Intae Jung
  • Function : Author
Paul R. Shapiro
  • Function : Author
Taha Dawoodbhoy
  • Function : Author
Jenny G. Sorce
  • Function : Author
  • PersonId : 1218626
  • IdHAL : jennygsorce
Ilian T. Iliev
  • Function : Author

Abstract

During reionization, a fraction of galactic Lyα emission is scattered in the intergalactic medium (IGM) and appears as diffuse light extending megaparsecs from the source. We investigate how to probe the properties of the early galaxies and their surrounding IGM using this scattered light. We create a Monte Carlo algorithm to track individual photons and reproduce several test cases from previous literature. Then, we run our code on the simulated IGM of the CoDaII simulation. We find that the scattered light can leave an observable imprint on the emergent spectrum if collected over several square arcminutes. Scattering can redden the emission by increasing the path lengths of photons, but it can also make the photons bluer by upscattering them according to the peculiar motion of the scatterer. The photons emitted on the far blue side of the resonance appear more extended in both frequency and space compared to those emitted near the resonance. This provides a discriminating feature for the blueward emission, which cannot be constrained from the unscattered light coming directly from the source. The ionization state of the IGM also affects the scattered light spectrum. When the source is in a small H II region, the emission goes through more scatterings in the surrounding H I region regardless of the initial frequency and ends up more redshifted and spatially extended. This can result in a weakening of the scattered light toward high z during reionization. Our results provide a framework for interpreting the scattered light to be measured by high-z integral-field-unit surveys.
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Dates and versions

insu-03707834 , version 1 (29-06-2022)

Licence

Attribution - CC BY 4.0

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Hyunbae Park, Hyo Jeong Kim, Kyungjin Ahn, Hyunmi Song, Intae Jung, et al.. Scattering of Lyα Photons through the Reionizing Intergalactic Medium: I. Spectral Energy Distribution. The Astrophysical Journal, 2022, 931, ⟨10.3847/1538-4357/ac69e4⟩. ⟨insu-03707834⟩
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