Panel a: ⟨δμ_9G⟩ (r mag) vs. mass-weighted stellar age (Gyr) for the bulgecomponent of our sample LTGs. The solid line shows a linear fit to the data. Panel b: logarithm of the stellar mass (M_⊙) in the bulge vs. mass-weighted stellar age (Gyr). Galaxies spectroscopically classified as Seyfert and LINER are marked. Panel c: total stellar mass vs. . The solid and dashed lines show, respectively, a linear fit to the data and equality between both quantities. Panel d: logarithm of vs. mass-weighted stellar metallicity (Z_⊙). Panel e: logarithm of vs. logarithm of the mean stellar surface density Σ_⋆,B (M_⊙ kpc⁻²) in the bulge. The gray-shaded quadrant at log 10 and log Σ_⋆,B ≥ 9 delineates the parameter space containing 93% of all Seyfert and LINER galaxies in our sample. Panel f: spectroscopic classification after BPT within simulated 3^′′ SDSS fibers (method a in Sect. 2.3; cf. Fig. 4).