SF-03-0022

Massive star formation scenario in the LMC probed by the ALMA ACA Molecular Cloud Survey

Kisetsu Tsuge, Yasuo Fukui, Kosuke Higashino, Kazuki Tokuda, Toshikazu Onishi, Hidetoshi Sano, Ayu Konishi, Kengo Tachihara, Rin Yamada, Kazuyuki Muraoka, Tony Wong, Marta Sewilo, Rosie Chen, Suzanne Madden, Remy Indebetouw, Tsuyoshi Inoue, Akiko Kawamura, Vianney Lebouteiller, Margaret Meixner, Tetsuhiro Minamidani, Norikazu Mizuno, Omnarayani Nayak, Atsushi Nishimura, Kazuya Saigo, Sarolta Zahorecz, Manami Sasaki

HI gas collisions at 50-100 km/s triggered by galactic tidal interactions between the Large and Small Magellanic Clouds (the LMC and SMC, respectively) are proposed to be a cluster formation process. In N159 in the southeastern part of the LMC, oriented filamentary molecular clouds were identified, corresponding to the direction of HI collisions. This suggests that kpc-scale HI gas collisions have induced the formation of filamentary clouds with a width of 0.1 pc. In this study, we focus on N44, N11, and N79, where evidence for HI collisions has been found, and investigate the universality and variety of molecular cloud formation. The collision velocities of HI gas in N44, N11, and N79 are 70, 50, and 30 km/s, respectively, and the pressures of collisional compression are 14, 11, and 4 [10^5 K /cm^3], respectively. We found that there is a correlation between the pressure and the number of high-mass stars formed. Furthermore, filamentary molecular clouds were identified on the pc scale by the ALMA Cycle8 2021 molecular cloud survey (PI: K., Tsuge). The velocity dispersion, 13CO/12CO intensity ratio, mass, and filament aspect ratio were compared among the three regions, revealing that N44 had the highest values, followed by N11 and N79. The results show that N44 > N11 > N79 for all physical properties. These features suggest that more intense HI gas collisions possibly create a higher-pressure environment and promote the formation of more massive, denser, more filamentary, and more complex velocity structures, leading to the efficient formation of high-mass stars.