Average FWHM distribution of emission lines: we show the distribution of all significant Hβ and Mg ii emission lines. The bimodal FWHM distribution implies the presence of two species: narrow line emitters (⁠|$\rm FHWM<1000\,\rm km\,s^{-1}$|⁠) and broad line emitters (⁠|$\rm FHWM\ge 1000\,\rm km\,s^{-1}$|⁠).