Left panel: the galaxy spectrum (black line) is compared to the fitted linear combination of template stellar spectra (red line) and emission lines (blue line). The green dots show the residuals. Right panel: age and metallicity obtained from the spectral fitting. The color scale refers to the mass fraction in each bin of age and metallicity. The red dot represents the mass-weighted age ⟨ t / Gyr ⟩ _M and the mass-weighted metallicity ⟨[M/H]⟩ _M.