Year: 1999
Type: article
Abstract: We have developed an improved recombination calculation of H, He I, and He II in the early universe that involves a line-by-line treatment of each atomic level. We find two major differences compared with previous calculations. First, the ionization fraction x e is approximately 10% smaller for redshifts ≲800 because of nonequilibrium processes in the excited states of H. Second, He I recombination is much slower than previously thought, and it is delayed until just before H recombines. We describe the basic physics behind the new results and present a simple way to reproduce our calculation. This should enable a fast computation of the ionization history (and of the quantities such as the power spectrum of cosmic microwave background anisotropies that depend on it) for arbitrary cosmologies, without the need to consider the hundreds of atomic levels used in our complete model.
Source: The Astrophysical Journal
DOI: 10.1086/312250
Authors: S. Seager, D. D. Sasselov, D. Scott
Institutions: Harvard University, University of British Columbia
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2152404335