Q branch of the fundamental rovibrational ν₂ band of H₃⁺ (P and R branches are shown in Fig. C.1). The JWST/NIRSpec spectra are continuum-subtracted (Sect. 2.3) and scaled. The H₃⁺ transitions are labeled at the top of the panel and indicated by the dotted black vertical lines. Dashed and dot-dashed gray vertical lines indicate transitions of H₂ and H I, respectively. The number below the region name is the scaling factor applied. In this figure, the rest frame is defined by the velocity of the H₃⁺ features. We note that the JWST/NIRSpec spectra have a ∼0.1 μm gap centered around 4.05–4.15 μm that partially affects the Q branch of some of these regions. For IRAS 08572, we masked spectral channels with highly uncertain flux values.