Overview of the first 7 sources in order of RID except for RID = 4764 and 5479. Each row shows a different object. Panels a–f: are the same as those of Fig. 2. Panel a: MID = 0 means that no MUSE ID is assigned in the MXDF catalog (i.e., ZCONF = 0). Panels d and e: the spectral slices used to produce the optimized NB are indicated by the yellow and orange shaded areas for sources with high S/N spectral slices at r = r_in − r_CoG and those with low S/N spectral slices at r = r_in − r_CoG, respectively (see Sect. 3.2). We note that the emission ring shown in the NB of RID = 7876 is caused by the mask for a source with extended emission. Since the ring is located outside r_CoG, it does not affect our results.