Issue |
A&A
Volume 392, Number 2, September III 2002
|
|
---|---|---|
Page(s) | 691 - 698 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20020942 | |
Published online | 30 August 2002 |
Submillimeter dust emission of the M 17 complex measured with PRONAOS
1
Centre d'Étude Spatiale des Rayonnements, 9 Av. du colonel Roche, BP 4346, 31028 Toulouse Cedex 4, France
2
Institut d'Astrophysique Spatiale, Campus d'Orsay, Bât. 121, 15 rue Clémenceau, 91405 Orsay Cedex, France
3
LERMA, Observatoire de Paris, 61 avenue de l'Observatoire, 75014 Paris, France
4
Service d'Aéronomie du CNRS, BP 3, 91371 Verrières-le-Buisson Cedex, France
Corresponding author: X. Dupac, dupac@cesr.fr
Received:
15
January
2002
Accepted:
12
June
2002
We map a 50 area in and around the M 17 molecular complex
with the French submillimeter balloon-borne telescope PRONAOS, in order to
better understand the thermal emission of cosmic dust and the structure of
the interstellar medium.
The PRONAOS-SPM instrument has an angular resolution of
about 3', corresponding to a size of 2 pc at the distance of this complex,
and a high sensitivity up to 0.8 MJy/sr.
The observations are made in four wide submillimeter bands corresponding to effective wavelengths
of 200
, 260
, 360
and 580
.
Using an improved map-making method for PRONAOS data, we map the M 17
complex and faint condensations near the dense warm core.
We derive maps of both the dust temperature and the spectral index, which vary
over a wide range, from about 10 K to 100 K for the temperature and from about 1
to 2.5 for the spectral index.
We show that these parameters are anticorrelated, the
cold areas (10–20 K) having a spectral index around 2, whereas the warm
areas have a spectral index between 1 and 1.5.
We discuss possible causes of this effect, and we propose an
explanation involving intrinsic variations of the grain properties.
Indeed, to match the observed spectra with two dust components having a spectral index equal to 2 leads to very large and unlikely amounts of cold dust.
We also give estimates of the column densities and masses of the studied
clumps.
Three cold clumps (14–17 K) could be gravitationally unstable.
Key words: dust / infrared: ISM: continuum / ISM: clouds / ISM: individual (M 17)
© ESO, 2002
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