Mass-age and mass metallicity distributions colour-coded by the median value of the χ_min² for estimates based on the Exp_FixZ_BC03_STELIB model library (same as in G05 and G21, left panels) and the SanCB19_MILES model library (reference models in this work, right panels). See Table 1 for more details about the SPS models. The black and green lines identify the density levels enclosing 16%, 50%, 84%, and 97.5% of the complete galaxy sample. The dotted horizontal lines in the mass-metallicity planes indicate the solar metallicity of Z_⊙ ≡ 0.02.