Distribution of the intensities of emission-dominaed (left panels) and absorption-dominated (right panels) spectra cases of Fig. 1. The red solid lines show the KDE for different kernel widths: (top) Silverman’s rule, (middle) kernel with of rms (=1 K), and (bottom) kernel width one tenth of the rms (=0.1 K). The continuum level determined as the position of the maximum of the KDE is indicated in each panel.