Effect of Radiative Feedbacks for Resonant Transitions during Cosmological Recombination

Abstract

The inhibition of the total HI $n\leftrightarrow 1$ transition rate by delayed resonant reabsorption of HI $(n+1)\to 1$ photons by HI $n\to 1$ line which is possible due to cosmological redshift is considered semi-analytically. The method taking into account this effect in the frame of simple three-level approximation model of recombination is suggested. It is confirmed that the resonant feedbacks affect ionization fraction at the level about 0.2% for the epoch of last scattering. Similar consideration of HeI $2^{1}P\leftrightarrow 1^{1}S$ $\Rightarrow$ HeI $2^{3}P\leftrightarrow 1^{1}S$ feedback for helium is provided. It is confirmed that allowance of this feedback leads to increase of predicted free electron fraction by 0.12% at $z\simeq 2300$. It is shown that taking into account absorption and thermalization of HeI $2^{1}P\leftrightarrow 1^{1}S$ resonant superequilibrium photons (during their redshifting to the HeI $2^{3}P\leftrightarrow 1^{1}S$ frequency) by small amount of neutral hydrogen ($10^{-7}-10^{-4}$ of total number of hydrogen atoms and ions) existing in helium recombination epoch is important for correct consideration of this helium feedback.

22 pages, 11 figures, 1 table

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Cited by in corpus (9)

• The Cosmology of Atomic Dark Matter
• HyRec: A fast and highly accurate primordial hydrogen and helium recombination code
• Ultrafast effective multi-level atom method for primordial hydrogen recombination
• Recombinations to the Rydberg States of Hydrogen and Their Effect During the Cosmological Recombination Epoch
• HYREC-2: a highly accurate sub-millisecond recombination code
• How sound are our ultra-light axion approximations?
• Radiative transfer effects in primordial hydrogen recombination
• Molecular hydrogen in the cosmic recombination epoch
• Advanced Three Level Approximation for Numerical Treatment of Cosmological Recombination