Upper panel: dependence of and on redshift as described by the best-fit power-law X = n ⋅ (1 + z)^−γ, with its 1σ uncertainty. Lower panel: dependence of and on redshift. These two plots represent a synthetic description of the cosmic evolution of the iron abundance obtained in this work. The curves and shaded areas have been already shown in the right panels of Fig. 11 and the upper panels of Fig. 12.