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HyRec: A fast and highly accurate primordial hydrogen and helium recombination code

Ali-Haїmoud, Yacine and Hirata, Christopher M. (2011) HyRec: A fast and highly accurate primordial hydrogen and helium recombination code. Physical Review D, 83 (4). Art. No. 043513. ISSN 1550-7998.

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We present a state-of-the-art primordial recombination code, HYREC, including all the physical effects that have been shown to significantly affect recombination. The computation of helium recombination includes simple analytic treatments of hydrogen continuum opacity in the He I 2^1P^o - 1^1S line, the He I] 2^3P^o - 1^1S line, and treats feedback between these lines within the on-the-spot approximation. Hydrogen recombination is computed using the effective multilevel atom method, virtually accounting for an infinite number of excited states. We account for two-photon transitions from 2s and higher levels as well as frequency diffusion in Lyman-α with a full radiative transfer calculation. We present a new method to evolve the radiation field simultaneously with the level populations and the free electron fraction. These computations are sped up by taking advantage of the particular sparseness pattern of the equations describing the radiative transfer. The computation time for a full recombination history is ~2 seconds. This makes our code well suited for inclusion in Monte Carlo Markov chains for cosmological parameter estimation from upcoming high-precision cosmic microwave background anisotropy measurements.

Item Type:Article
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Hirata, Christopher M.0000-0002-2951-4932
Additional Information:© 2011 American Physical Society. Received 20 November 2010; published 15 February 2011. The authors thank Jens Chluba for stimulating conversations on the physics of recombination and Daniel Grin for carefully reading the manuscript of this paper. Y. A-H. and C. H. are supported by the U.S. Department of Energy (Contract No. DE-FG03-92-ER40701) and the National Science Foundation (Contract No. AST-0807337). C. H. is supported by the Alfred P. Sloan Foundation and the David & Lucile Packard Foundation.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG03-92-ER40701
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Issue or Number:4
Classification Code:PACS: 98.80.-k, 95.30.Jx, 32.80.Rm, 98.70.Vc
Record Number:CaltechAUTHORS:20110307-093938930
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Official Citation:HyRec: A fast and highly accurate primordial hydrogen and helium recombination code Yacine Ali-Haïmoud and Christopher M. Hirata Published 15 February 2011 (24 pages) 043513
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22677
Deposited By: Ruth Sustaita
Deposited On:08 Mar 2011 18:57
Last Modified:03 Oct 2019 02:39

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