Absorption effects in the expanding Universe: spectral transmittance functions of the intergalactic medium for distant sources

Anguohao Yang, Bohdan Novosyadlyj, Bohdan Melekh +1

We construct two self-consistent analytic approximations to the neutral hydrogen fraction, $x_{\mathrm{HI}}(z)$, and the helium ionization fractions, $x_{\mathrm{HeI}}(z)$, $x_{\mathrm{HeII}}(z)$…