Letter to the Editor
ISO observations of the reflection nebula Ced 201: evolution of carbonaceous dust *
D. Cesarsky 1,2,
J. Lequeux 3,
C. Ryter 4 and
M. Gérin 5
Received 30 November 1999 / Accepted 28 January 2000
We present spectrophotometric imaging mid-IR observations of the reflection nebula Ced 201. Ced 201 is a part of a molecular cloud illuminated by a B9.5V star moving through it at more than 12 km s-1. The spectra of Ced 201 give evidence for transformation of very small carbonaceous grains into the carriers of the Aromatic Infrared Bands (AIBs), due to the radiation field of the illuminating star and/or to shock waves created by its motion. These very small grains emit mainly very broad bands and a continuum. We suggest that they are present everywhere in the interstellar medium but can only be detected in the mid-IR under special circumstances such as those prevailing in this reflection nebula. The efficiency of energy conversion of stellar light into mid-infrared emission is 7.5% for both the very small grains and the AIB carriers, and the fraction of interstellar carbon locked in these emitters is approximately 15%.
Key words: ISM: individual objects: Ced 201 ISM: dust, extinction infrared: ISM: lines and bands
* Based on observations at the Cal Tech submillimeter observatory (CSO) and with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.
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© European Southern Observatory (ESO) 2000
Online publication: February 25, 2000