q parameter as a function of redshift, z, for galaxies with different stellar mass, M_⋆, as given in the colorbar. The reference model compared to the observed data set of Delvecchio et al. (2021) is presented in the middle panel. In panels from left to right, the magnetic field strength in the model is increased; see the discussion around Eq. (14) for the parameters f_B and f_turb. From bottom to top, the ionization degree is increased via the parameter f_ion which affects the free-free emission; see Sect. 2.3.2.