Diagram of the model we adopted to add the emission lines to the spectra in PRISMA. The inset top panel shows the spectrum produced by stellar populations older than 10 Myr, which only depends on the CB19 stellar population synthesis models. The inset bottom panel displays the spectrum produced by stellar populations, which includes the CB19 SED models, and incorporates the nebular emission that is produced by the ionized gas cloud, which is represented by a sphere of radius R.