Left panels: fraction of the total luminosity in lines relative to the accretion luminosity, i.e. the continuum excess luminosity. The light blue region corresponds to the range of values found in Alcalá et al. (2014). Right panels: total luminosity from the lines as a function of the log L_acc as indicated in the labels. The blue line in each panel corresponds to our best fit, while the light-blue lines give an indication of the spread of the fit (see Sect. 3.4). The dashed gray lines show the one-to-one relation. Red circled black dots correspond to sources where the Brγ line is detected.