1996A&A...308..895L

Using the Canada-France-Hawaii telescope to observe the reflection nebula NGC 7023, we have obtained a 0.8" spatial resolution image of vibrationally excited H₂ in the v=1-0S(1) line at 2.121mm and in the v=1-0S(2) line at 2.033mm. As in earlier observations of H₂ IR fluorescence in NGC 2023 (Field et al. 1994), the image shows narrow filamentary structure. These structures show spatial correlations, but also anti-correlations, with the structure of extended red emission (ERE), with implications for the mechanism of ERE. Spatial variations in the S(1) emission and in the ratio of S(1) to S(2) emission are found in regions lying within a one to a few arcseconds of each other. This is interpreted in terms of small scale structures in the gas in the H₂ emission zone, on a scale of 0.004pc or less. Our most recent models of VUV excitation of H₂ IR fluorescence, by light from a nearby star, give a good estimate for the observed peak brightness in the v=1-0S(1) line.