1996A&A...315L.305C

We present spectrophotometric observations of the reflection nebula NGC 7023 obtained with the ISOCAM Circular Variable Filter (CVF) in the spectral range 5.15 to 16.5µm. Maps in the 16µm continuum emission and in the Unidentified Infrared Bands (UIBs) have been obtained. The continuum emission peaks at the dense interface between the surrounding molecular cloud and the inner photodissociated region. The whole spectrum (UIBs and continuum) becomes systematically harder closer to the exciting star. Our observations show that it is entirely due to the same category of carriers, probably PAHs heated transiently by single photons, and that the systematic spectral changes inside NGC 7023 are due to changes in the size distribution or/and ionization degree of these particles.