Fraction of PAHs models. a) Emitting region water column density for dust-to-gas mass ratio models; this region comprises 15−85% of the radially and vertically integrated flux. Green vertical dotted lines distinguish the reservoirs. b) Theoretical Spitzer SH/LH modules spectra (R = 600) for a dust-to-gas model series, continuum subtracted, and arbitrarily shifted. c) Average extension of the line emitting region, which comprises 50% of the line flux radially and vertically for 12.407 μm. d) Average extension of the line emitting region, which comprises 50% of the line flux radially and vertically for 538.29 μm.