Fit of the Hβ line with different functions. The original spectrum is the solid black line, the residuals of the model subtractions are the solid blue line, the horizontal dashed black line represents the zero level of continuum, and the vertical dashed line represents the rest-frame wavelength of Hβ. The values of and d.o.f. for each fit are shown in the top left corner of each figure. Top left: fit with a single Gaussian function, represented by the red dot-dashed line. Top right: fit with a single Lorentzian function, indicated by the dot-dashed red line. Bottom left: fit with a Lorentzian function, indicated by the dashed green line, and a narrow Gaussian function, represented by the dashed orange line. The best fit is indicated by the dot-dashed red line. Bottom right: fit with three Gaussian functions, indicated by the dashed green, purple, and orange lines. The narrow component is the orange function. The best fit is indicated by the dot-dashed red line.