12.7/11.3 μm PAH EW ratio versus PAH EW(11.3). Left panel: EW plot for the HERUS sample. Open blue circles correspond to group of 2 ULIRGs. Right panel: EW plot for the CON-quest sample. Labelled sources correspond to those galaxies classified as CONs in Falstad et al. (2021). Colour-coded stars, circles, and squares represent the strength of the 9.7 μm silicate feature of ULIRGs, LIRGs, and subLIRGs, respectively. Colour-coded symbols correspond to the strength of the 9.7 μm silicate feature. The grey solid and dashed horizontal lines correspond to the average and 3σ values found by Hernán-Caballero et al. (2020) for star-forming galaxies. Finally, the green dotted lines represent constant values of the 12.7 μm PAH EW (0.03, 0.10 and 0.30).