Top: stacked SEDs for the PSB groups identified in the Meusinger et al. (2017) catalog. Groups 1, 2, and 3 are shown from top to bottom. Prior to stacking, the SEDs were normalized by the mean flux in the 5050–5150 Å region to account for redshift dependences (identical continua were assumed). All SEDs were given equal weight, but only spectra with a signal-to-noise ratio > 5 for the g, r, and i bands were included (this includes > 97% of the galaxies in the catalog). 16^th and 84^th percentiles are shown within the shaded area, and selected spectral lines are highlighted. Bottom: flux ratios.