PAH EW diagram (García-Bernete et al. 2022a) of the 12.7/11.3 PAH features against the 6.2/11.3 PAH features obtained from fitting the star-forming sample (top left; Hernán-Caballero et al. 2020), CONquest (top right; Falstad et al. 2021), HERUS (bottom left; Farrah et al. 2013), and GOALS (bottom right; Armus et al. 2009). Points in red have a nuclear optical depth τ_N > 3.5, and for the CONquest sample the triangle points are those identified as CONs by Σ_HCN-vib > 1 L_⊙ pc⁻². The grey lines show the mean values for the star-forming sample, with the 2σ values for the 12.7/11.3 PAH shown by the dashed lines. The purple shaded area shows the CON selection region.