The present day spectrum of the extragalactic background light (EBL) in UV, optical and IR wavelengths is the integral result of multiple astrophysical processes going on throughout the evolution of the Universe. The relevant processes include star formation, stellar evolution, light absorption and emission by the cosmic dust. The properties of these processes are known with uncertainties which contribute to the EBL spectrum precision. In the present paper we develop a numerical model of the EBL spectrum while maintaining the explicit dependence on the astrophysical parameters involved. We constructed a Markov Chain in the parameter space by using the likelihood function built with the up-to-date upper and lower bounds on the EBL intensity. The posterior distributions built with the Markov Chain Monte Carlo method are used to determine an allowed range of the individual parameters of the model. Consequently, the star formation rate multiplication factor is constrained in the range 1.01 < C sfr < 1.69 at 68% C.L. The method also results in the bounds on the lifetime, radius, dust particle density and opacity of the molecular clouds that have large ambiguity otherwise. It is shown that there is a reasonable agreement between the model and the intensity bounds while the astrophysical parameters of the best fit model are close to their estimates from literature.

A primordial magnetic field with strength in the 1–10 pG range can resolve the tension between different measurements of the Hubble constant and provide an explanation for the excess opacity in the 21 cm line at redshift 15 < z < 20 if it is present during the recombination and reionization epochs. This field can also survive in the voids of the large-scale structure in the present day universe. We study the sensitivity reach of the gamma-ray technique for measurement of such a relatively strong cosmological magnetic field using deep exposure(s) of the nearest hard spectrum blazar(s) with CTA telescopes. We show that the gamma-ray measurement method can sense the primordial magnetic field with a strength of up to 10−11 G. Combination of the cosmic microwave background and gamma-ray constraints can thus sense the full range of possible cosmological magnetic fields to confirm or rule out their relevance to the problem of the origin of cosmic magnetic fields, as well as their influence on recombination and reionization epochs.