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TwitterA&A 482, 197-208 (2008)
DOI: 10.1051/0004-6361:20078769
Submillimeter line emission from LMC N159W: a dense, clumpy PDR in a low metallicity environment
J. L. Pineda1, N. Mizuno2, J. Stutzki3, M. Cubick3, M. Aravena1, F. Bensch1, F. Bertoldi1, L. Bronfman4, K. Fujishita2, U. U. Graf3, M. Hitschfeld3, N. Honingh3, H. Jakob3, K. Jacobs3, A. Kawamura2, U. Klein1, C. Kramer3, J. May4, M. Miller3, Y. Mizuno2, P. Müller1, T. Onishi2, V. Ossenkopf3, D. Rabanus3, M. Röllig1, M. Rubio4, H. Sasago2, R. Schieder3, R. Simon3, K. Sun3, N. Volgenau3, H. Yamamoto2, and Y. Fukui21 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: jopineda@astro.uni-bonn.de
2 Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
3 KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
4 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
(Received 1 October 2007 / Accepted 29 January 2008)
Abstract
Context. Star formation at earlier cosmological times took place in an
interstellar medium with low metallicity. The Large Magellanic Cloud
(LMC) is ideally suited to study star formation in such an environment.
Aims. The physical and chemical state of the ISM in a star forming environment
can be constrained by observations of submm and FIR spectral lines of the
main carbon carrying species, CO, C I and C II, which originate
in the surface layers of molecular clouds illuminated by the UV radiation
of the newly formed, young stars.
Methods. We present high-angular resolution sub-millimeter observations in the
N159W region in the LMC obtained with the NANTEN2 telescope of the
12CO J = 4 
3, J = 7 6, and 13CO J = 4 3 rotational and [C I] 3P1-3P0 and 3P2-3P1
fine-structure transitions. The 13CO J = 4 3 and [C I] 3P2-3P1 transitions are detected for the first time in
the LMC. We derive the physical and chemical properties of the
low-metallicity molecular gas using an escape probability code and a
self-consistent solution of the chemistry and thermal balance of the
gas in the framework of a clumpy cloud PDR model.
Results. The separate excitation analysis of the submm CO lines and the carbon
fine structure lines shows that the emitting gas in the N159W region
has temperatures of about 80 K and densities of about
104 cm-3. The estimated C to CO abundance ratio close to
unity is substantially higher than in dense massive star-forming
regions in the Milky Way. The analysis of all observed lines
together, including the [C II] line intensity reported in the
literature, in the context of a clumpy cloud PDR model constrains the
UV intensity to about
220 and an average density of
the clump ensemble of about 105 cm-3, thus confirming
the presence of high density material in the LMC N159W region.
Key words: astrochemistry -- ISM: molecules -- ISM: clouds -- ISM: individual objects: N 159W
© ESO 2008