a1 Department of Astronomy, Ohio State University
a2 Jet Propulsion Laboratory, California Institute of Technology
a3 Spitzer Science Center, California Institute of Technology
a4 Ritter Astrophysical Research Center, University of Toledo
a5 University of Arizona
a6 Université de Toulouse, UPS, CESR
The fullerene C60 has four infrared active vibrational transitions at 7.0, 8.5, 17.5 and 18.9 μm. We have previously observed emission features at 17.4 and 18.9 μm in the reflection nebula NGC 7023 and demonstrated spatial correlations suggestive of a common origin. We now confirm the identification of these features with C60 by detecting a third emission feature at 7.04 ± 0.05μm at a position of strong 18.9 μm emission in NGC 7023. We also report the detection of these three features in the reflection nebula NGC 2023. We show with spectroscopic mapping of NGC 7023 that the 18.9 μm feature peaks on the central star, that the 16.4 μm emission feature due to PAHs peaks between the star and a nearby photodissociation front, and that the 17.4 μm feature is a blend of a PAH feature and C60. The derived C60 abundance is consistent with that from previous upper limits and possible fullerene detections in the interstellar medium.
(Online publication March 30 2011)