Issue |
A&A
Volume 461, Number 3, January III 2007
|
|
---|---|---|
Page(s) | 999 - 1012 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20065855 | |
Published online | 16 October 2006 |
The cooling of atomic and molecular gas in DR21
1
KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany e-mail: jakob@ph1.uni-koeln.de
2
SAp/CEA Saclay, 91191 Gif-sur-Yvette, France
3
Observatoire de Bordeaux, Université de Bordeaux 1, BP 89, 33270 Floirac, France
4
SRON, National Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
Received:
19
June
2006
Accepted:
11
September
2006
Aims. We present an overview of a high-mass star formation region through the major (sub-)mm, and far-infrared cooling lines to gain insight into the physical conditions and the energy budget of the molecular cloud.
Methods.
We used the KOSMA 3 m telescope to map the core
() of the Galactic star-forming region DR21/DR21 (OH) in the Cygnus X region
in the two fine structure lines of atomic carbon (
and
), in four mid-J
transitions of CO and 13CO, and in CS
.
These observations were combined with FCRAO
observations of 13CO and C18O.
Five positions, including DR21, DR21 (OH), and DR21 FIR1, were observed
with the ISO/LWS grating spectrometer in the [
] 63 and 145 μm lines, the [
]
158 μm line, and four high-J CO lines. We discuss the intensities
and line ratios at these positions and apply the local thermal equilibrium (LTE)
and non-LTE analysis methods in order to
derive physical parameters such as mass, density and temperature.
The CO line emission was modeled up to
.
Results.
From non-LTE modeling of the low- to high-J CO lines, we identify two gas components, a cold one at temperatures of
K and
one with
K at a local clump density of about n(H2) ~
cm-3.
While the cold quiescent component is massive, typically containing more than 94% of the mass, the warm,
dense, and turbulent gas is dominated by mid- and high-J CO line emission and its large line widths.
The medium must be clumpy with a volume-filling of a few percent.
The CO lines are found to be important in cooling the cold molecular gas, e.g. at DR21 (OH).
Near the outflow of the UV-heated source DR21, the gas cooling is dominated by line emission of atomic oxygen
and of CO.
Atomic and ionised carbon play a minor role.
Key words: ISM: clouds / ISM: abundances / radio lines: ISM / line: profiles / stars: formation / ISM: individual objects: DR21 / ISM: individual objects: DR21 (OH)
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.