Illustration of the decomposition of the 8.6 μm PAH band. Top: normalized profiles of the redshifted profile representing class ℬ (the first component), the blueshifted profile representing class 𝒜 (the transitional profile), the derived second component used in the decomposition, and the extracted 8.35 μm feature. Bottom: typical decomposition of the 8.6 μm band with components 1 and 2, and the 8.35 μm feature.