Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ISO observations of the reflection nebula Ced 201: evolution of
  carbonaceous dust   We present spectrophotometric imaging mid-IR observations of the reflection
nebula Ced201. Ced201 is a part of a molecular cloud illuminated by a B9.5V
star moving through it at more than 12 km/s. The spectra of Ced201 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%.

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The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom