FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN): Molecular clouds toward W 33; possible evidence for a cloud–cloud collision triggering O star formation. (11th January 2018)

• Record Type: Journal Article
• Authors: Kohno, Mikito; Torii, Kazufumi; Tachihara, Kengo; Umemoto, Tomofumi; Minamidani, Tetsuhiro; Nishimura, Atsushi; Fujita, Shinji; Matsuo, Mitsuhiro; Yamagishi, Mitsuyoshi; Tsuda, Yuya; Kuriki, Mika; Kuno, Nario; Ohama, Akio; Hattori, Yusuke; Sano, Hidetoshi; Yamamoto, Hiroaki; Fukui, Yasuo
• Is Part Of: Publications of the Astronomical Society of Japan. Volume 70:Number SP2(2018)
• Publication Date: 2018-01-11
• Subjects: ISM: clouds -- ISM: individual objects (W 33) -- ISM: molecules -- stars: formation; Astronomy -- Periodicals; 520.5
• DOI: 10.1093/pasj/psx137
• Languages: English
• ISSNs: 0004-6264

Abstract

Abstract: We observed molecular clouds in the W 33 high-mass star-forming region associated with compact and extended H ii regions using the NANTEN2 telescope as well as the Nobeyama 45 m telescope in the J = 1–0 transitions of 12 CO, 13 CO, and C 18 O as part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN) legacy survey. We detected three velocity components at 35 km s −1, 45 km s −1, and 58 km s −1 . The 35 km s −1 and 58 km s −1 clouds are likely to be physically associated with W 33 because of the enhanced 12 CO J = 3–2 to J = 1–0 intensity ratio as $R_{\rm 3\mbox{-}2/1\mbox{-}0} > 1.0$ due to the ultraviolet irradiation by OB stars, and morphological correspondence between the distributions of molecular gas and the infrared and radio continuum emissions excited by high-mass stars. The two clouds show complementary distributions around W 33. The velocity separation is too large to be gravitationally bound, and yet not explained by expanding motion by stellar feedback. Therefore, we discuss whether a cloud–cloud collision scenario likely explains the high-mass star formation in W 33.