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arXiv · 1908.08404

ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions

Hidetoshi Sano·Kisetsu Tsuge·Kazuki Tokuda·Kazuyuki Muraoka·Kengo Tachihara·Yumiko Yamane·Mikito Kohno·Shinji Fujita·Rei Enokiya·Gavin Rowell·Nigel Maxted·Miroslav D. Filipovic·Jonathan Knies·Manami Sasaki·Toshikazu Onishi·Paul P. Plucinsky·Yasuo Fukui
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Abstract

We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M33 using $^{12}$CO($J$ = 2-1), $^{13}$CO($J$ = 2-1), and C$^{18}$O($J$ = 2-1) line emission at a spatial resolution of $\sim$2 pc. There are two individual molecular clouds with a systematic velocity difference of $\sim$6 km s$^{-1}$. Three continuum sources representing up to $\sim$10 high-mass stars with the spectral types of B0V-O7.5V are embedded within the densest parts of molecular clouds bright in the C$^{18}$O($J$ = 2-1) line emission. The two molecular clouds show a complementary spatial distribution with a spatial displacement of $\sim$6.2 pc, and show a V-shaped structure in the position-velocity diagram. These observational features traced by CO and its isotopes are consistent with those in high-mass star-forming regions created by cloud-cloud collisions in the Galactic and Magellanic Cloud HII regions. Our new finding in M33 indicates that the cloud-cloud collision is a promising process to trigger high-mass star formation in the Local Group.

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Hidetoshi Sano, Kisetsu Tsuge, Kazuki Tokuda, Kazuyuki Muraoka, Kengo Tachihara, Yumiko Yamane, Mikito Kohno, Shinji Fujita, Rei Enokiya, Gavin Rowell, Nigel Maxted, Miroslav D. Filipovic, Jonathan Knies, Manami Sasaki, Toshikazu Onishi, Paul P. Plucinsky, Yasuo Fukui. 2019-08-22. ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions. https://doi.org/10.1093/pasj/psaa045

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