Comparison between the different properties of the Hβ emission line profile. Left panel: FWHM(Hβ_BC) vs. FWHM of the full Hβ profile. Central panel: velocity centroid at 1/2 intensity c(1/2) vs. FWHM(Hβ_full). Right panel: velocity centroid at 1/4 flux intensity c(1/4) vs. FWHM(Hβ_full). Symbols surrounded by open circles show the radio-loud sources and filled circles represent the radio-quiet from the sample. Red line represent the linear regression performed for Pop. B. Horizontal dashed lines in the central and right panels indicate c(1/4) = 0 and c(1/2) = 0 for Hβ, respectively. Purple vertical dashed lines shows the boundary between Pop. A and Pop. B. The many MS spectral type (ST) are represented in different colours: A1 (•); A2 (•); A3 (•); B1 (•); and B2 (•).