Baryonic structural relations for passive galaxies: M_bar vs. R_50, bar (top left), M_bar vs. Σ_50, bar (bottom left), and R_50, bar vs. Σ_bar vs. (bottom right). See Sect. 2 for references to the various datasets of Es, S0s, dEs/dSphs, and UDGs. We also considered the ‘classical’ bulges of Sa-Sc galaxies. The mean uncertainties of our sample galaxies are indicated in the top corner of each panel. For all these objects, the baryonic structural relations are virtually the same as the stellar ones. The dashed grey lines show the selection criteria of UDGs from van Dokkum et al. (2015).