Same as Fig. 8 for joint fit on [O III] emission line of galaxy #399 from GLASS survey observed with a roll angle of 52° (left panels) and 152° (right panels). It should be noted that for the first spectrogram, the large residual structure, which is visible at the bottom of the results from an incomplete source decontamination does not significantly affect the model adjustment result, but only increases the final χ² value. The decrease in the joint χ² corresponds to a 25.5 σ-level detection.