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Radiative transfer effects in primordial hydrogen recombination

Ali-Haïmoud, Yacine and Grin, Daniel and Hirata, Christopher M. (2010) Radiative transfer effects in primordial hydrogen recombination. Physical Review D, 82 (12). Art. No. 123502. ISSN 1550-7998.

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The calculation of a highly accurate cosmological recombination history has been the object of particular attention recently, as it constitutes the major theoretical uncertainty when predicting the angular power spectrum of cosmic microwave background anisotropies. Lyman transitions, in particular the Lyman-α line, have long been recognized as one of the bottlenecks of recombination, due to their very low escape probabilities. The Sobolev approximation does not describe radiative transfer in the vicinity of Lyman lines to a sufficient degree of accuracy, and several corrections have already been computed in other works. In this paper, we compute the impact of some radiative transfer effects that were previously ignored, or for which previous treatments were incomplete. First, the effect of Thomson scattering in the vicinity of the Lyman-α line is evaluated, using a full redistribution kernel incorporated into a radiative transfer code. The effect of feedback of distortions generated by the optically thick deuterium Lyman-α line blueward of the hydrogen line is investigated with an analytic approximation. It is shown that both effects are negligible during cosmological hydrogen recombination. Second, the importance of high-lying, nonoverlapping Lyman transitions is assessed. It is shown that escape from lines above Lyγ and frequency diffusion in Lyβ and higher lines can be neglected without loss of accuracy. Third, a formalism generalizing the Sobolev approximation is developed to account for the overlap of the high-lying Lyman lines, which is shown to lead to negligible changes to the recombination history. Finally, the possibility of a cosmological hydrogen recombination maser is investigated. It is shown that there is no such maser in the purely radiative treatment presented here.

Item Type:Article
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URLURL TypeDescription Paper
Hirata, Christopher M.0000-0002-2951-4932
Additional Information:© 2010 The American Physical Society. (Received 4 October 2010; published 1 December 2010) The authors thank Jens Chluba for useful discussions about Thomson scattering in Lyman-α and acknowledge fruitful conversations with the participants of the July 2009 Paris Workshop on Cosmological Recombination. Y. A-H. and C. H. are supported by the U.S. Department of Energy (DE-FG03-92-ER40701) and the National Science Foundation (AST-0807337). D. G. is supported by the Dan David Foundation, the Gordon and Betty Moore Foundation, and the National Science Foundation (AST-0807044). C. H. is supported by the Alfred P. Sloan Foundation.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-92-ER40701
Dan David FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Issue or Number:12
Classification Code:PACS numbers: 98.80.Es, 32.80.Rm, 98.62.Ra, 98.70.Vc
Record Number:CaltechAUTHORS:20170408-151302755
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76044
Deposited By: 1Science Import
Deposited On:16 May 2017 23:12
Last Modified:03 Oct 2019 16:57

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