Lyman-{alpha} transfer in primordial hydrogen recombination

Journal Article · Wed Jul 15 04:00:00 EDT 2009 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.80.023001· OSTI ID:21316175

Hirata, Christopher M; Forbes, John ^[1]

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1. Caltech M/C 350-17, Pasadena, California 91125 (United States)

Cosmological constraints from the cosmic microwave background (CMB) anisotropies rely on accurate theoretical calculations of the cosmic recombination history. Recent work has emphasized the importance of radiative transfer calculations due to the high optical depth in the H i Lyman lines. Transfer in the Ly{alpha} line is dominated by true emission and absorption, Hubble expansion, and resonant scattering. Resonant scattering causes photons to diffuse in frequency due to random kicks from the thermal velocities of hydrogen atoms, and also to drift toward lower frequencies due to energy loss via atomic recoil. Past analyses of Ly{alpha} transfer during the recombination era have either considered a subset of these processes, ignored time dependence, or incorrectly assumed identical emission and absorption profiles. We present here a fully time-dependent radiative transfer calculation of the Ly{alpha} line including all of these processes, and compare it to previous results that ignored the resonant scattering. We find a faster recombination due to recoil enhancement of the Ly{alpha} escape rate, leading to a reduction in the free electron density of 0.45% at z=900. This results in an increase in the small-scale CMB power spectrum that is negligible for the current data but will be a 0.9{sigma} correction for Planck. We discuss the reasons why we find a smaller correction than some other recent computations.

• OSTI ID: 21316175
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 2 Vol. 80; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
ABSORPTION
ANISOTROPY
ATOMS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CORRECTIONS
COSMOLOGICAL MODELS
ELECTRON DENSITY
EMISSION
ENERGY LOSSES
HYDROGEN
LYMAN LINES
PHOTONS
RADIANT HEAT TRANSFER
RECOMBINATION
RELICT RADIATION
RESONANCE SCATTERING
SPECTRA
TIME DEPENDENCE