Molecular line mapping of the giant molecular cloud associated with RCW 106 – II. Column density and dynamical state of the clumps |
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| Authors: | T Wong E F Ladd D Brisbin M G Burton I Bains M R Cunningham N Lo P A Jones K L Thomas S N Longmore A Vigan B Mookerjea C Kramer Y Fukui A Kawamura |
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| Institution: | School of Physics, University of New South Wales, Sydney, NSW 2052, Australia;Astronomy Department, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA;CSIRO Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia;Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA;Department of Astronomy, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853, USA;Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia;Physics &Astronomy Department, University of Kentucky, Lexington, KY 40506, USA;Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA;KOSMA, I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany;Department of Astronomy &Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai, India;Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan |
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| Abstract: | We present a fully sampled C18O (1–0) map towards the southern giant molecular cloud (GMC) associated with the H ii region RCW 106, and use it in combination with previous 13CO (1–0) mapping to estimate the gas column density as a function of position and velocity. We find localized regions of significant 13CO optical depth in the northern part of the cloud, with several of the high-opacity clouds in this region likely associated with a limb-brightened shell around the H ii region G333.6?0.2. Optical depth corrections broaden the distribution of column densities in the cloud, yielding a lognormal distribution as predicted by simulations of turbulence. Decomposing the 13CO and C18O data cubes into clumps, we find relatively weak correlations between size and linewidth, and a more sensitive dependence of luminosity on size than would be predicted by a constant average column density. The clump mass spectrum has a slope near ?1.7, consistent with previous studies. The most massive clumps appear to have gravitational binding energies well in excess of virial equilibrium; we discuss possible explanations, which include magnetic support and neglect of time-varying surface terms in the virial theorem. Unlike molecular clouds as a whole, the clumps within the RCW 106 GMC, while elongated, appear to show random orientations with respect to the Galactic plane. |
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| Keywords: | stars: formation ISM: clouds ISM: molecules ISM: structure |
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