Spatial variation of the cooling lines in the reflection nebula NGC 7023 J. Bernard-Salas, E. Habart, M. Köhler, A. Abergel, H. Arab, V. Lebouteiller, C. Pinto, M. H. D. van der Wiel, G. J. White and M. Hoffmann A&A, 574 (2015) A97 Published online: 30 January 2015 DOI: 10.1051/0004-6361/201423705