Tsukuba Uchu Forum

147th Uchu Forum

Star formation induced by cloud-cloud collisions in nearby barred galaxies

Yoshiomasa Watanabe

Sibaura Institute of Technology


Abstract
More than 300 molecular species have been identified in the interstellar matter. These chemical compositions provide various insights into the physical condition of molecular gas, its surrounding environment, and its evolution in the star and planet formation studies in the Galaxy. Thanks to the recent high sensitivity and high spatial resolution observations with ALMA, we can also apply the chemical approach to the star formation studies in the nearby galaxies. In this talk, we will present how cloud-cloud collisions affect star formation by using multi-line observations toward nearby barred spiral galaxies at a scale of sub-kpc with ALMA. In the bar-end region of the nearby galaxy NGC 3627, the shock tracer CH$_3$OH is strongly enhanced at the collision of two molecular clouds. From the distribution of the dense gas tracer N$_2$H$^+$, the PDR tracer CN, and 3 mm continuum emission, we found that dense gas formation and star formation occur in a short timescale of < a few My after the collision. In addition, we also found that the star formation activities are induced by the cloud-cloud collisions in downstream of the bar in M83. Recent galaxy-scale star formation simulation demonstrates that star formation induced by cloud-cloud collisions has a significant role in global star formation (Horie et al. 2024). Therefore, it would be more and more important to study star formation induced by cloud-cloud collisions in nearby galaxies with the aid of chemical compositions. Image