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Tracing the cold molecular gas reservoir through dust emission in the SMC

Published online by Cambridge University Press:  01 July 2008

Caroline Bot
Affiliation:
UMR7550, Observatoire Astronomique de Strasbourg, F-67000 Strasbourg, France email: [email protected]
Mónica Rubio
Affiliation:
Departamento de Astronomia, Universidad de Chile, Casilla 36-Dm Santiago, Chile
François Boulanger
Affiliation:
Institut d'Astrophysique Spatiale, Université de Paris-Sud, F-91405, Orsay, France
Marcus Albrecht
Affiliation:
Argelander-Institut für Astronomie, Universität Bonn, Germany Universidad Católica del Norte, Chile
Frank Bertoldi
Affiliation:
Argelander-Institut für Astronomie, Universität Bonn, Germany
Alberto D. Bolatto
Affiliation:
University of Maryland, MD, USA
Adam K. Leroy
Affiliation:
Max Planck Institute for Astronomy, Heidelberg, Germany
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Abstract

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The amount of molecular gas is a key for understanding the future star formation in a galaxy. However, this quantity is difficult to infer as the cold H2 is almost impossible to observe and, especially at low metallicities, CO only traces part of the clouds, keeping large envelopes of H2 hidden from observations. In this context, millimeter dust emission tracing the cold and dense regions can be used as a tracer to unveil the total molecular gas masses. I present studies of a sample of giant molecular clouds in the Small Magellanic Cloud. These clouds have been observed in the millimeter and sub-millimeter continuum of dust emission: with SIMBA/SEST at 1.2 mm and the new LABOCA bolometer on APEX at 870 μm. Combining these with radio data for each cloud, the spectral energy distribution of dust emission are obtained and gas masses are inferred. The molecular cloud masses are found to be systematically larger than the virial masses deduced from CO emission. Therefore, the molecular gas mass in the SMC has been underestimated by CO observations, even through the dynamical masses. This result confirms what was previously observed by Bot et al. (2007). We discuss possible interpretations of the mass discrepancy observed: in the giant molecular clouds of the SMC, part of cloud's support against gravity could be given by a magnetic field. Alternatively, the inclusion of surface terms in the virial theorem for turbulent clouds could reproduce the observed results and the giant molecular clouds could be transient structures.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2009

References

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