Panel a: logarithm of the total stellar mass (M_⊙) vs. mass-weighted stellar age (Gyr) of the bulge and disk component (large and small dots, respectively). Linear fits to the data for the bulge and the disk are shown with solid lines. The color coding is the same as in Fig. 6. Panel b: log() vs. mass-weighted stellar metallicity (Z_⊙) for the bulge and the disk. The layout is identical to that in panel a. Panel c: log() vs. age contrast δt_BD ( – ) (Gyr) between bulge and disk. Panel d: log() vs. metallicity contrast δZ_BD ( – ) in Z_⊙ between bulge and disk.