Fitting results of nine neighbouring spectra in the GRS test field for the decomposition with GAUSSPY (a) and after Stage 1–3 of GAUSSPY+ (b–d, respectively). Individual fit components and their combination are shown in dashed and solid black lines, respectively. Horizontal dashed black lines mark a S/N threshold of 3 and blue shaded areas indicate the identified signal intervals. The number of used fit components N_comp and the resulting AICc values are noted in the upper right corner of the main panel. The smaller subpanels show the residual with the horizontal dotted black lines marking values of ±σ_rms.