Primordial helium recombination. I. Feedback, line transfer, and continuum opacity
Journal Article
·
· Physical Review. D, Particles Fields
- Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)
Precision measurements of the cosmic microwave background temperature anisotropy on scales l>500 will be available in the near future. Successful interpretation of these data is dependent on a detailed understanding of the damping tail and cosmological recombination of both hydrogen and helium. This paper and two companion papers are devoted to a precise calculation of helium recombination. We discuss several aspects of the standard recombination picture, and then include feedback, radiative transfer in He i lines with partial redistribution, and continuum opacity from H i photoionization. In agreement with past calculations, we find that He ii recombination proceeds in Saha equilibrium, whereas He i recombination is delayed relative to Saha due to the low rates connecting excited states of He i to the ground state. However, we find that at z<2200 the continuum absorption by the rapidly increasing H i population becomes effective at destroying photons in the He i 2{sup 1}P{sup o}-1{sup 1}S line, causing He i recombination to finish around z{approx_equal}1800, much earlier than previously estimated.
- OSTI ID:
- 21249993
- Journal Information:
- Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 8 Vol. 77; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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