Line ratios diagram used to compute the extinction. Blue points are the observed line ratios of Paβ/Paα and [Fe II]λ1.257 μm/[Fe II]λ1.644 μm. Dashed lines fit extinction values computed assuming theoretical line ratios based on the Cardelli et al. (1989) extinction law and different electronic temperatures and densities (as indicated). The symbols along the model lines mark optical extinction values in steps of A_V = 1, increasing from right to left.