Abstract:

Gaseous media in the universe are essential to both galaxy evolution and the growth of supermassive black holes. In this talk, I will introduce two distinct projects we have undertaken that each focus on gaseous environments through different observational approaches. The first part focuses on the gaseous environment in the vicinity of active galactic nuclei (AGNs). In this project, we utilized the infrared flux variability, which is characteristic of the AGN, to distinguish between dusty gas and dust-free gas components around the AGN for the first time, and discussed the radiation-pressure effect on these different gas structures. I will also present our recent results on variability analysis of the broad Halpha line for local AGNs with unique characteristics uncovered by our independent analysis. The second part focuses on the gaseous environment in submillimeter galaxies (SMGs). In this project, we performed [CII]158µm observations using ALMA for 16 flux-limited SMGs at z = 3-5, originally detected by the SCUBA-2 survey. Thanks to the bright nature of our sample, we successfully detected the [CII] line with S/N>10. Most of the detected [CII] lines exhibit complex profiles that reflect the kinematics of [CII]-emitting gas. Here, I will present our results regarding comparisons between [CII] luminosity and physical properties, such as star formation rate and molecular gas mass, as well as comparisons between [CII] and CO line profiles and analyses of the [CII] physical size.