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NRO Legacy Project: Survey of Giant Molecular Clouds in M33

Published online by Cambridge University Press:  21 October 2010

N. Kuno
Affiliation:
Nobeyama Radio Observatory, National Astronomical Observatory of Japan Graduate University for Advanced Studies (SOKENDAI), Japan
T. Tosaki
Affiliation:
Joetsu University of Education, Japan
S. Onodera
Affiliation:
Nobeyama Radio Observatory, National Astronomical Observatory of Japan
K. Muraoka
Affiliation:
Osaka Prefecture University, Japan
H. Kaneko
Affiliation:
Graduate University for Advanced Studies (SOKENDAI), Japan
T. Sawada
Affiliation:
National Astronomical Observatory of Japan
K. Nakanishi
Affiliation:
Graduate University for Advanced Studies (SOKENDAI), Japan National Astronomical Observatory of Japan
S. Komugi
Affiliation:
Insititute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
Y. Tamura
Affiliation:
University of Tokyo, Japan
K. Kohno
Affiliation:
University of Tokyo, Japan
R. Kawabe
Affiliation:
Nobeyama Radio Observatory, National Astronomical Observatory of Japan
N. Arimoto
Affiliation:
Graduate University for Advanced Studies (SOKENDAI), Japan National Astronomical Observatory of Japan
S. Okamoto
Affiliation:
University of Tokyo, Japan
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As the Nobeyama Radio Observatory Legacy Project: Survey of Giant Molecular Clouds in M33, we have been mapping M33 in CO(1-0) with the multi-beam receiver BEARS equipped on the 45-m telescope using the OTF mapping technique since 2007. The purpose of this project is to investigate the physical properties of GMCs and understand the evolutionary process from GMC formation to star formation in GMCs by comparing with various data such as CO(3-2), 1.1 mm continuum obtained with ASTE10m telescope at Atacama and the optical data obtained with SUBARU. We identified 87 GMCs using the first year data of CO(1-0) and observed 28 GMCs among them in CO(3-2) with ASTE (Onodera 2009, PhD thesis, University of Tokyo). From the comparison of these lines, it was shown that the CO(3-2)/CO(1-0) ratio increases with star forming activity in the GMCs. Furthermore, we found that more massive GMCs tend to have higher CO(3-2)/CO(1-0) ratio. Since the ratio is thought to be an indicator of the fraction of warm and dense molecular gas, our results imply that the fraction of warm and dense gas increases with GMC mass. Especially, since the ratio in the GMCs with low star forming activity is in the range where the ratio depends mainly on the density, we speculate that dense gas fraction increases with GMC mass.

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Contributed Papers
Copyright
Copyright © International Astronomical Union 2010