Carnegie-Irvine Galaxy Survey VII. S0 galaxies

Many S0s do not host prominent bulges. S0s have a broad distribution of bulge-to-total ratios (B/T) and Sersic indices (n), with average values of B/T=0.34+/-0.15 and n=2.62+/-1.02, qualitatively consistent with the notion that S0s define a parallel sequence with and may have evolved from spiral galaxies.

This is further reinforced by the incidence of bars and lenses in S0s, which, when compared with the statistics in spirals, supports the idea that lenses are demised bars. However, despite their wide range of prominence, the bulges of S0s form a surprisingly uniform sequence on both the Kormendy and fundamental plane relations. There is no evidence for population dichotomy or other indications of differentiation into classical and pseudo bulges.