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Fig. 6


Top panel: the emission of the size (11.2/3.3 μm) and ionization map as a function of distance to the star in NGC 7023 (see Fig. 2). The region of the crosscut is the white rectangle is Fig. 1. In the bottom panel, along exactly the same region of the top panel, the normalized intensity of the neutral PAHs, ionised PAHs, and the VSGs is plotted (Berné et al. 2007). The vertical dashed line is the peak of the H2 emission (see Fig. 2). The PDR surface is 48 arcsec from the star, where the 11.2/3.3 μm ratio and the neutral PAH emission are maximum and the VSG emission starts to decline. The increase in VSG abundance for less then 25 arcsec (dashed) is an artifact and reflects emission from big grains in radiative equilibrium, rather than thermally fluctuating VSGs.

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