The distribution of warm gas in the G327.3–0.6 massive star-forming region
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69,
2 Univ. de Bordeaux, LAB, UMR 5804, 33270 Floirac, France
3 CNRS, LAB, UMR 5804, 33270 Floirac, France
4 SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
5 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
6 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
7 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
Received: 4 February 2012
Accepted: 9 November 2012
Aims. Most studies of high-mass star formation focus on massive and/or luminous clumps, but the physical properties of their larger scale environment are poorly known. In this work, we aim at characterising the effects of clustered star formation and feedback of massive stars on the surrounding medium by studying the distribution of warm gas through mid-J12CO and 13CO observations.
Methods. We present APEX 12CO(6–5), (7–6), 13CO(6–5), (8–7) and HIFI 13CO(10–9) maps of the star forming region G327.36–0.6 with a linear size of ~3 pc × 4 pc. We infer the physical properties of the emitting gas on large scales through a local thermodynamic equilibrium analysis, while we apply a more sophisticated large velocity gradient approach on selected positions.
Results. Maps of all lines are dominated in intensity by the photon dominated region around the Hii region G327.3–0.5. Mid-J12CO emission is detected over the whole extent of the maps with excitation temperatures ranging from 20 K up to 80 K in the gas around the Hii region, and H2 column densities from few 1021 cm-2 in the inter-clump gas to 3 × 1022 cm-2 towards the hot core G327.3–0.6. The warm gas (traced by 12 and 13CO(6–5) emission) is only a small percentage (~10%) of the total gas in the infrared dark cloud, while it reaches values up to ~35% of the total gas in the ring surrounding the Hii region. The 12CO ladders are qualitatively compatible with photon dominated region models for high density gas, but the much weaker than predicted 13CO emission suggests that it comes from a large number of clumps along the line of sight. All lines are detected in the inter-clump gas when averaged over a large region with an equivalent radius of 50′′(~0.8 pc), implying that the mid-J12CO and 13CO inter-clump emission is due to high density components with low filling factor. Finally, the detection of the 13CO(10–9) line allows to disentangle the effects of gas temperature and gas density on the CO emission, which are degenerate in the APEX observations alone.
Key words: stars: formation / HII regions / ISM: individual objects: G327.3 / 0.6
© ESO, 2013