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arXiv · 1808.00709

Molecular gas in a Spitzer bubble N4: possible evidence for cloud-cloud collisions as a trigger of massive star formation

Shinji Fujita·Kazufumi Torii·Kengo Tachihara·Rei Enokiya·Katsuhiro Hayashi·Nario Kuno·Mikito Kohno·Tomoka Tosaki·Mitsuyoshi Yamagishi·Atsushi Nishimura·Tomofumi Umemoto·Tetsuhiro Minamidani·Mitsuhiro Matsuo·Yuya Tsuda·Hidetoshi Sano·Daichi Tsutsumi·Akio Ohama·Satoshi Yoshiike·Kazuki Okawa·Yasuo Fukui·Other Fugin Members
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Abstract

Herein, we present the 12CO (J=1-0) and 13CO (J=1-0) emission line observations via the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) toward a Spitzer bubble N4. We observed clouds of three discrete velocities: 16, 19, and 25 km/s. Their masses were 0.1x10^4 Msun, 0.3x10^4 Msun, and 1.4x10^4 Msun, respectively. The distribution of the 25-km/s cloud likely traces the ring-like structure observed at mid-infrared wavelength. We could not find clear expanding motion of the molecular gas in N4. On the contrary, we found a bridge feature and a complementary distribution, which are discussed as observational signatures of a cloud-cloud collision, between the 16- and 25-km/s clouds. We proposed a possible scenario wherein the formation of a massive star in N4 was triggered by a collision between the two clouds; however whereas the 19-km/s cloud is possibly not a part of the interaction with N4. The time scale of collision is estimated to be 0.2-0.3 Myr, which is comparable to the estimated dynamical age of the HII region of ~0.4 Myr. In N4W, a star-forming clump located west of N4, we observed molecular outflows from young stellar objects and the observational signature of a cloud-cloud collision. Thus, we also proposed a possible scenario in which massive- or intermediate-mass star formation was triggered via a cloud-cloud collision in N4W.

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Shinji Fujita, Kazufumi Torii, Kengo Tachihara, Rei Enokiya, Katsuhiro Hayashi, Nario Kuno, Mikito Kohno, Tomoka Tosaki, Mitsuyoshi Yamagishi, Atsushi Nishimura, Tomofumi Umemoto, Tetsuhiro Minamidani, Mitsuhiro Matsuo, Yuya Tsuda, Hidetoshi Sano, Daichi Tsutsumi, Akio Ohama, Satoshi Yoshiike, Kazuki Okawa, Yasuo Fukui, Other Fugin Members. 2018-08-02. Molecular gas in a Spitzer bubble N4: possible evidence for cloud-cloud collisions as a trigger of massive star formation. https://doi.org/10.3847/1538-4357/aafac5

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