Astron. Astrophys. 347, 949-956 (1999)

Upper limit on and features in the ISO-SWS spectrum of the reflection nebula NGC 7023 ^*

C. Moutou ¹, K. Sellgren ², L. Verstraete ³ and A. Léger <sup>3

1</sup> European Southern Observatory, Alonso de Cordoba 3107, Santiago, Chile (cmoutou@eso.org)
² Astronomy Department, Ohio State University, 174 West 18th Avenue, Columbus OH 43210, USA (sellgren@astronomy.ohio-state.edu)
³ Institut d'Astrophysique Spatiale, CNRS, Université Paris Sud, bâtiment 121, F-91405 Orsay, France (leger@iaslab.ias.fr; verstra@ias.fr)

Received 26 January 1999 / Accepted 28 May 1999

Abstract

We present here the 7.0-8.7 µm spectrum of the bright reflection nebula NGC 7023. Our observations are made with the Short Wavelength Spectrometer (SWS) on the European satellite Infrared Space Observatory (ISO). The vibrational bands of the ionized fullerene are expected at 7.11 and 7.51 µm, while those of the neutral fullerene C₆₀ are expected at 7.0 and 8.45 µm. We estimate an upper limit in NGC 7023 for the abundance of 0.26% of the interstellar abundance of carbon, while C₆₀ contains 0.27% of interstellar carbon.

Key words: ISM: dust, extinction ISM: lines and bands ISM: molecules

* ISO is an ESA project with instruments funded by ESA Member States (especially the PI countries: the United Kingdom, France, the Netherlands, Germany), and with the participation of ISAS and NASA.

Send offprint requests to: C. Moutou

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Contents

• 1. C₆₀ and related compounds in the interstellar medium
• 2. Abundance of from its electronic transitions
• 3. in the infrared
• 4. Observations and data reduction
• 5. Estimate of the upper limit
  • 5.1. Assumptions
  • 5.2. Case A
  • 5.3. Case B
  • 5.4. Comparison of abundances from different methods
  • 5.5. Neutral C₆₀
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: June 6, 1999
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