Title

Cloud structures in M 17 SWex : Possible cloud–cloud collision

Authors

Shinichi W. Kinoshita, University of Tokyo
Fumitaka Nakamura, University of Tokyo
Quang Nguyen-Luong, McMaster University
Benjamin Wu, National Astronomical Observatory of Japan
Tonomi Shimoikura, Otsuma Women's University
Koji Sugitani, Nagoya City University
Kazuhito Dobashi, Tokyo Gakugei University
Hideaki Takemura, National Astronomical Observatory of Japan
Patricio Sanhueza, National Astronomical Observatory of Japan
Kee-Tae Kim, University of Science and Technology, Korea
Hyunwoo Kang, Korea Astronomy & Space Institute
Neal J. Evans, University of Texas at Austin
Glenn J. White, The Open University
Cassandra Fallscheer, Central Washington UniversityFollow

Document Type

Article

Department or Administrative Unit

Physics

Publication Date

6-26-2020

Abstract

Using wide-field ¹³CO (J = 1−0) data taken with the Nobeyama 45 m telescope, we investigate cloud structures of the infrared dark cloud complex in M 17 with Spectral Clustering for Interstellar Molecular Emission Segmentation. In total, we identified 118 clouds that include 11 large clouds with radii larger than 1 pc. The clouds are mainly distributed in the two representative velocity ranges of 10–20 km s⁻¹ and 30–40 km s⁻¹. By comparing this with the ATLASGAL catalog, we found that the majority of the ¹³CO clouds with 10–20 km s⁻¹ and 30–40 km s⁻¹ are likely located at distances of 2 kpc (Sagittarius arm) and 3 kpc (Scutum arm), respectively. Analyzing the spatial configuration of the identified clouds and their velocity structures, we attempt to reveal the origin of the cloud structure in this region. Here we discuss three possibilities: (1) overlapping with different velocities, (2) cloud oscillation, and (3) cloud–cloud collision. In the position–velocity diagrams, we found spatially extended faint emission between ∼20 km s⁻¹ and ∼35 km s⁻¹, which is mainly distributed in the spatially overlapped areas of the clouds. Additionally, the cloud complex system is unlikely to be gravitationally bound. We also found that in some areas where clouds with different velocities overlapped, the magnetic field orientation changes abruptly. The distribution of the diffuse emission in the position–position–velocity space and the bending magnetic fields appear to favor the cloud–cloud collision scenario compared to other scenarios. In the cloud–cloud collision scenario, we propose that two ∼35 km s⁻¹ foreground clouds are colliding with clouds at ∼20 km s⁻¹ with a relative velocity of 15 km s⁻¹. These clouds may be substructures of two larger clouds having velocities of ∼35 km s⁻¹ (≳10³ M_⊙) and ∼20 km s⁻¹ (≳10⁴ M_⊙), respectively.

Comments

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Recommended Citation

Kinoshita, S. W., Nakamura, F., Nguyen-Luong, Q., Wu, B., Shimoikura, T., Sugitani, K., Dobashi, K., Takemura, H., Sanhueza, P., Kim, K. T., Kang, H., Evans, N. J., White, G. J., & Fallscheer, C. (2020). Cloud structures in M 17 SWex : Possible cloud–cloud collision. Publications of the Astronomical Society of Japan, 73(Supplement 1), S300–S320. https://doi.org/10.1093/pasj/psaa053

Journal

Publications of the Astronomical Society of Japan

Rights

© The Author(s) 2020. Published by Oxford University Press on behalf of the Astronomical Society of Japan.