Dynamics of Primordial Hydrogen Recombination with Allowance for a Recoil for Scattering in the Ly-alpha Line

TL;DR

This paper investigates how including recoil effects and nonstationary radiative transfer in Ly-alpha line scattering influences primordial hydrogen recombination, showing that these factors accelerate recombination and affect cosmic microwave background spectra.

Contribution

It introduces a detailed analysis of recoil and nonstationarity effects in Ly-alpha radiative transfer, revealing their significant impact on hydrogen recombination dynamics.

Findings

Recoil effects accelerate hydrogen recombination by over 1%.

Corrections to CMB spectra reach 1.1% for TT and 1.7% for EE.

Nonstationary radiative transfer further speeds up recombination.

Abstract

It is shown that taking into account a recoil for radiation scattering in the Ly-alpha line can lead to a noticable acceleration of primordial hydrogen recombination. Thus for LambdaCDM model a decrease of ionization degree exceeds 1% for redshifts z in a range 800 - 1050 achieving approximately 1.3% at z=900. Corresponding corrections to the cosmic microwave background power spectra can achieve 1.1% for TT spectra and 1.7% for EE ones. Radiative transfer in these calculations was treated in a quasistationary approximation. Numerical solutions are also obtained in diffusion approximation for a nonstationary problem of Ly-alpha line radiative transfer under partial frequency redistribution with a recoil. An evolution of a local line profile is traced to as well as an evolution of a relative number of uncompensated transitions from 2p state down to 1s one. It is shown that taking into account nonstationarity of Ly-alpha line radiative transfer can lead to an additional acceleration of primordial hydrogen recombination.