PAH ratio maps of NGC 7023 NW PDR. The colors correspond to the 11.2/3.3 μm emission ratio on the left (PAH size tracer) and to the 8.0/11.2 μm ratio on the right (PAH ionization indication). Top panels: the contour lines represent the H2 emission (Lemaire et al. 1996) where the contours range from 0.8 to 3.7 [Wm-2 sr-1] with 5 steps. Middle panels: the contour lines are the ERE emission. The contours are spaced in 5 steps with the outermost contour line of 0.5 and a maximum of 1.0 (Arb. Units) (Berné et al. 2008). Pixels with an S/N smaller than 3 in the ratio have been discarded. Bottom panel: The IRAC 8.0 μm image with the contours of the 11.2/3.3 μm ratio.
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