EDP Sciences
Free access
Volume 424, Number 3, September IV 2004
Page(s) 887 - 903
Section Interstellar and circumstellar matter
DOI http://dx.doi.org/10.1051/0004-6361:20047085

A&A 424, 887-903 (2004)
DOI: 10.1051/0004-6361:20047085

Emission of CO, C I, and C II in W3 Main

C. Kramer1, H. Jakob1, B. Mookerjea1, N. Schneider2, M. Brüll1 and J. Stutzki1

1  KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
    e-mail: lastname@ph1.uni-koeln.de
2  Observatoire de Bordeaux, Université de Bordeaux 1, BP 89, 33270 Floirac, France
    e-mail: schneider@obs.u-bordeaux1.fr

(Received 16 January 2004 / Accepted 3 June 2004 )

We used the KOSMA 3m telescope to map the core 7'  $\times$ 5' of the Galactic massive star forming region W3 Main in the two fine structure lines of atomic carbon and four mid- J transitions of CO and  13CO. The maps are centered on the luminous infrared source IRS 5 for which we obtained ISO/LWS data comprising four high- J CO transitions, [ $\ion{C}{ii}$], and [ $\ion{O}{i}$] at  63 and  $145~\mu$m. In combination with a KAO map of integrated line intensities of [ $\ion{C}{ii}$] (Howe et al. 1991), this data set allows us to study the physical structure of the molecular cloud interface regions where the occurence of carbon is believed to change from C + to C 0, and to CO. The molecular gas in W3 Main is warmed by the far ultraviolet (FUV) field created by more than a dozen OB stars. Detailed modelling shows that most of the observed line intensity ratios and absolute intensities are consistent with a clumpy photon dominated region (PDR) of a few hundred unresolved clumps per 0.84 pc beam, filling between 3 and 9% of the volume, with a typical clump radius of 0.025 pc ( 2.2''), and typical mass of 0.44  $M_{\odot}$. The high-excitation lines of CO stem from a  100-200 K layer, as do the [ $\ion{C}{i}$] lines. The bulk of the gas mass is however at lower temperatures.

Key words: infrared: ISM -- ISM: clouds -- ISM: structure -- ISM: abundances -- galaxies: ISM -- submillimeter

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