Propagation of the burst of radiation in expanding and recombining Universe: Thomson scattering

TL;DR

This study models how an instantaneous burst of radiation propagates through an expanding, recombining universe considering Thomson scattering, revealing that high-redshift bursts produce narrow, highly polarized signals with weak dependence on initial conditions.

Contribution

It provides a detailed analysis of radiation burst propagation in a cosmological context, highlighting the effects of Thomson scattering on intensity and polarization distributions.

Findings

Intensity profiles are weakly dependent on initial conditions for z0 > 1400.

Angular distributions are narrow, about 3-5 arcminutes.

Polarization can reach up to 70%, with an average around 15%.

Abstract

Within the framework of a flat cosmological model a propagation of an instantaneous burst of nonpolarized isotropic radiation is considered from the moment of its beginning at some initial redshift z0 to the moment of its registration now (at z=0). Thomson (Rayleigh) scattering by free electrons is considered as the only source of opacity. Spatial distributions of the mean (over directions) radiation intensity are calculated as well as angular distributions of radiation intensity and polarization at some different distances from the center of the burst. It is shown that for redshifts z0 large enough (z0 > 1400) the profile of the mean intensity normalized to the total number of photons emitted during the burst weakly depends on initial conditions (say the moment z0 of the burst, the width and shape of initial radiation distribution in space). As regards angular distributions of intensity and polarization they turn to be rather narrow (3 - 5 arcmin) while polarization can reach 70%. On the average an expected polarization can be about 15%.