The jet and arc molecular clouds toward westerlund 2, RCW 49, and hess J1023-575; 12CO and 13CO (J = 2-1 and J = 1-0) observations with nanten2 and mopra telescope

N. Furukawa, A. Ohama, T. Fukuda, K. Torii, T. Hayakawa, H. Sano, T. Okuda, H. Yamamoto, N. Moribe, A. Mizuno, H. Maezawa, T. Onishi, A. Kawamura, N. Mizuno, J. R. Dawson, T. M. Dame, Y. Yonekura, F. Aharonian, E. De Oña Wilhelmi, G. P. RowellR. Matsumoto, Y. Asahina, Y. Fukui

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We have made new CO observations of two molecular clouds, which we call jet and arc clouds, toward the stellar cluster Westerlund 2 and the TeV γ-ray source HESS J1023-575. The jet cloud shows a linear structure from the position of Westerlund 2 on the east. In addition, we have found a new counter jet cloud on the west. The arc cloud shows a crescent shape in the west of HESS J1023-575. A sign of star formation is found at the edge of the jet cloud and gives a constraint on the age of the jet cloud to be Myr. An analysis with the multi CO transitions gives temperature as high as 20 K in a few places of the jet cloud, suggesting that some additional heating may be operating locally. The new TeV γ-ray images by H.E.S.S. correspond to the jet and arc clouds spatially better than the giant molecular clouds associated with Westerlund 2. We suggest that the jet and arc clouds are not physically linked with Westerlund 2 but are located at a greater distance around 7.5 kpc. A microquasar with long-term activity may be able to offer a possible engine to form the jet and arc clouds and to produce the TeV γ-rays, although none of the known microquasars have a Myr age or steady TeV γ-rays. Alternatively, an anisotropic supernova explosion which occurred Myr ago may be able to form the jet and arc clouds, whereas the TeV γ-ray emission requires a microquasar formed after the explosion.

Original languageEnglish
Article number70
Pages (from-to)1-20
Number of pages20
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 1 Feb 2014
Externally publishedYes

Bibliographical note

Copyright 2014 The American Astronomical Society. First published in the Astrophysical Journal, 781(2), 70, 2014. The original publication is available at, published by IOP Publishing. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


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