Invited Presentation

Multi-line spectroscopy to assess molecular cloud properties

Author(s): Yuri Nishimura (The University of Tokyo / NAOJ)

Presenter: Yuri Nishimura (The University of Tokyo / NAOJ)

Spectral lines of various kinds of molecules such as HCN and HCO+ are now regularly detected in nearby galaxies. Owing to their chemical processes and high critical densities for emission, they have naively been employed as a proxy of dense gas content in unresolved molecular clouds. To test the validity of this assertion, understanding of the excitation condition and chemical abundance variation throughout the molecular cloud is essential. I will present multi-line observations of the nearby galaxy M51 and the Galactic star-forming cloud W3(OH), and discuss the characteristic density for the most common molecular emissions in the millimeter wavelengths.