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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

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posted on 2023-05-18, 07:39 authored by Furukawa, N, Ohama, A, Fukuda, T, Torii, K, Hayakawa, T, Sano, H, Okuda, T, Yamamoto, H, Moribe, N, Mizuno, A, Maezawa, H, Onishi, T, Kawamura, A, Mizuno, N, Joanne Dawson, Dame, TM, Yonekura, Y, Aharonian, F, De Ona Wilhelmi, E, Rowell, GP, Matsumoto, R, Asahina, Y, Fukui, Y
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.

History

Publication title

Astrophysical Journal

Volume

781

Article number

70

Number

70

Pagination

1-20

ISSN

0004-637X

Department/School

School of Natural Sciences

Publisher

Institute of Physics Publishing

Place of publication

1427 E 60Th St, Chicago, USA, Il, 60637-2954

Rights statement

Copyright 2014 The American Astronomical Society

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the physical sciences