Issue |
A&A
Volume 376, Number 3, September IV 2001
|
|
---|---|---|
Page(s) | 1064 - 1072 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20011032 | |
Published online | 15 September 2001 |
The physical conditions in the PDR of W49N*
1
CESR CNRS-UPS, BP 4346, 31028 Toulouse Cedex 04, France
2
Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
3
Observatoire de Bordeaux, 2 rue de l'Observatoire, BP 89, 33270 Floirac, France
4
Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 09, France
Corresponding author: C. Vastel, vastel@cesr.fr
Received:
24
April
2001
Accepted:
12
July
2001
We present ISO-LWS and ground-based SEST observations which probe the
Photo Dissociation Region (PDR) of W49N. The ISO-LWS observations consist of low
resolution (~200) grating spectra between 43 μm and 197 μm, and high
resolution (~104) Fabry-Pérot spectra of the [CII] 158 μm and
[OI] 63 and 145 μm lines. The SEST observations consist of C16O
and C18O
maps of the region.
Using all these observations and with the help of a detailed PDR model,
we have determined the physical and chemical structure of the PDR of W49N.
We find that only a tiny fraction, 2.5% , of the cloud gas is in the atomic form.
This gas has an average density
cm-3 and a temperature
K.
The PDR is created by a FUV field
times brighter than the average
FUV interstellar field, which is emitted by the stars associated with the several
HII regions inside the cloud. The photoelectric heating efficiency is very low,
~10-4, relative to other known PDRs, probably because of the relatively
high
ratio. Overall, W49N seems to be one of the youngest giant molecular
clouds actively forming stars in the Galaxy, since most of the cloud material is
still molecular and dense and not yet dispersed by the several embedded newly formed
massive protostars.
Key words: ISM: abundances / ISM: molecules / ISM: atoms / HII regions / ISM: individual objects: W49N
© ESO, 2001
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