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HCN Hyperfine Ratio Analysis of Massive Molecular Clumps

Published online by Cambridge University Press:  31 March 2017

William Schap ,
Peter Barnes ,
Adam Ginsburg  and
Antonio Ordonez
William Schap
Affiliation:
Astronomy Dept., University of Florida, PO Box 112055, Gainesville FL 32611, USA email: wschap@ufl.edu, pjb@ufl.edu, a.ordonez@astro.ufl.edu
Peter Barnes
Affiliation:
Astronomy Dept., University of Florida, PO Box 112055, Gainesville FL 32611, USA email: wschap@ufl.edu, pjb@ufl.edu, a.ordonez@astro.ufl.edu School of Science & Technology, University of New England, Armidale NSW 2351, Australia
Adam Ginsburg
Affiliation:
European Southern Observatory, Garching, Bavaria, Germany email: aginsbur@eso.org
Antonio Ordonez
Affiliation:
Astronomy Dept., University of Florida, PO Box 112055, Gainesville FL 32611, USA email: wschap@ufl.edu, pjb@ufl.edu, a.ordonez@astro.ufl.edu
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Abstract

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The CHaMP project has identified a uniform sample of 303 massive (20–8000 M⊙), dense (200–30,000 cm−3) molecular clumps in a large sector of the southern Milky Way that includes much of the Carina Arm. These are the kinds of clumps that are likely to be the precursors to IRDCs, large stellar clusters, and massive stars. We report new results of the physical conditions in these clouds based on the J=1 → 0 emission at 3mm from the HCN molecule. Analysis of the HCN emission from these clumps reveals that the physical conditions in the gas (i.e., the excitation temperature, optical depth, and column density) do not follow the molecular line emissivity in a straightforward way. This means that large fractions of the molecular material involved in massive cluster formation, while not completely“dark”, are under-luminous and easily missed in certain studies.

Keywords

Molecular cloudscluster formationstar formation
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S316: Formation, evolution, and survival of massive star clusters , August 2015 , pp. 131 - 132
Copyright
Copyright © International Astronomical Union 2017 

References

Barnes, P. J., Yonekura, Y., Fukui, Y., et al. 2011, ApJS, 196, 12 Google Scholar
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Ginsburg, A. & Mirocha, J. 2000, Astrophysics Source Code Library, 1109.001Google Scholar