Ratio between h_e the effective radius of the disk (or exponential) component and R_e the effective radius of the bulge (or Sérsic) component as a function of Hubble type (left) and B/T_g (right). The black dashed line in the left panel is the geometric mean value of this h_e/R_e ratio, and the vertical bars the estimated uncertainties on this mean (see Sect. 4.7.1 for details). Disk radii are on average 6 times larger than their bulge radii for lenticular galaxies. The size ratio increases along the Hubble sequence toward later and later spiral types, reaching ∼15 for Sbc, Sc and Scd types. This ratio is linked to the B/T_g luminosity bulge-to-total ratio, with higher values corresponding to relatively larger bulges, as highlighted by the linear fit (solid line, right panel). The dashed and dotted lines are the linear relations (in log–log scale) of h_e/R_e versus B/T_g derived from the two separate relations for h_e or R_e versus B/T_g obtained in Fig. 16 for Sa to Sm, and E to S0a types, respectively.