Quantifying Lyman-$α$ emissions from reionization fronts
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arXiv
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| Autori principali: | , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866917899800674304 |
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| author | Wilson, Bayu D'Aloisio, Anson Cain, Christopher Visbal, Eli Becker, George D. |
| author_facet | Wilson, Bayu D'Aloisio, Anson Cain, Christopher Visbal, Eli Becker, George D. |
| contents | During reionization, intergalactic ionization fronts (I-fronts) are sources of Ly$α$ line radiation produced by collisional excitation of hydrogen atoms within the fronts. In principle, detecting this emission could provide direct evidence for a reionizing intergalactic medium (IGM). In this paper, we use a suite of high-resolution one-dimensional radiative transfer simulations run on cosmological density fields to quantify the parameter space of I-front Ly$α$ emission. We find that the Ly$α$ production efficiency -- the ratio of emitted Ly$α$ flux to incident ionizing flux driving the front -- depends mainly on the I-front speed and the spectral index of the ionizing radiation. IGM density fluctuations on scales smaller than the typical I-front width produce scatter in the efficiency, but they do not significantly boost its mean value. The Ly$α$ flux emitted by an I-front is largest if 3 conditions are met simultaneously: (1) the incident ionizing flux is large; (2) the incident spectrum is hard, consisting of more energetic photons; (3) the I-front is traveling through a cosmological over-density, which causes it to propagate more slowly. We present a convenient parameterization of the efficiency in terms of I-front speed and incident spectral index. We make these results publicly available as an interpolation table and we provide a simple fitting function for a representative ionizing background spectrum. Our results can be applied as a sub-grid model for I-front Ly$α$ emissions in reionization simulations with spatial and/or temporal resolutions too coarse to resolve I-front structure. In a companion paper, we use our results to explore the possibility of directly imaging Ly$α$ emission around neutral islands during the last phases of reionization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_14622 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Quantifying Lyman-$α$ emissions from reionization fronts Wilson, Bayu D'Aloisio, Anson Cain, Christopher Visbal, Eli Becker, George D. Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies During reionization, intergalactic ionization fronts (I-fronts) are sources of Ly$α$ line radiation produced by collisional excitation of hydrogen atoms within the fronts. In principle, detecting this emission could provide direct evidence for a reionizing intergalactic medium (IGM). In this paper, we use a suite of high-resolution one-dimensional radiative transfer simulations run on cosmological density fields to quantify the parameter space of I-front Ly$α$ emission. We find that the Ly$α$ production efficiency -- the ratio of emitted Ly$α$ flux to incident ionizing flux driving the front -- depends mainly on the I-front speed and the spectral index of the ionizing radiation. IGM density fluctuations on scales smaller than the typical I-front width produce scatter in the efficiency, but they do not significantly boost its mean value. The Ly$α$ flux emitted by an I-front is largest if 3 conditions are met simultaneously: (1) the incident ionizing flux is large; (2) the incident spectrum is hard, consisting of more energetic photons; (3) the I-front is traveling through a cosmological over-density, which causes it to propagate more slowly. We present a convenient parameterization of the efficiency in terms of I-front speed and incident spectral index. We make these results publicly available as an interpolation table and we provide a simple fitting function for a representative ionizing background spectrum. Our results can be applied as a sub-grid model for I-front Ly$α$ emissions in reionization simulations with spatial and/or temporal resolutions too coarse to resolve I-front structure. In a companion paper, we use our results to explore the possibility of directly imaging Ly$α$ emission around neutral islands during the last phases of reionization. |
| title | Quantifying Lyman-$α$ emissions from reionization fronts |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2406.14622 |