Free Astronomy Magazine January-February 2024

39 JANUARY-FEBRUARY 2024 ASTRO PUBLISHING a much smaller region, especially within a few dozen light-years from the galactic center, has remained un- clear due to its minimal spatial scale. For instance, to quantitatively com- prehend the growth of black holes, it is necessary to measure the accre- tion flow rate (how much gas is flowing in) and to determine the amounts and types of gases (plasma, atomic gas, molecular gas) that are expelled as outflows at that small scale. Unfortunately, observational understanding in this regard has not progressed significantly until now, when the team led by Takuma Izumi, an assistant professor at the National Astronomical Observatory of Japan (affiliated with NAOJ and Tokyo Metropolitan University at the time of this study), has achieved a world-first success by quantita- tively measuring gas flows and their structures for all phases (plasma, atomic, and molecular) at a tiny spa- tial scale of just a few light-years around a supermassive black hole. Observations of multiphase gases can provide a more comprehensive understanding of the distribution and dynamics of matter around a black hole. The observed object was the Circinus Galaxy, a representative active ga- lactic nucleus in the nearby Universe. The achieved resolution was approx- imately one light-year. This marks the highest resolution achieved for multiphase gas observations in an active galactic nucleus. In this study, the research team ini- tially succeeded in capturing, for the first time, the accretion flow head- ing towards the supermassive black hole within the high-density gas disk extending over several light-years from the galactic center. Identifying this accretion flow had long been a challenging task due to the small scale of the region and the complex motions of gas near the galactic cen- ter. However, in this instance, the re- search team pinpointed where the foreground molecular gas was ab- sorbing the light from the back- ground brightly shining, active galactic nucleus. This identification was made possible through high- resolution observations with ALMA. Detailed analysis revealed that this absorbing material is moving in the direction away from us. Since the A n illustration depicting the distri- bution of interstellar medium in the active galactic nucleus based on the results of this observation. High- density molecular gas flows from the galaxy towards the black hole along the plane of the disk. The material accumulated around the black hole generates a tremendous amount of energy, causing the molecular gas to be destroyed and transformed into atomic and plasma phases. Most of these multiphase gases are expelled away via outflows from the nucleus (including plasma outflows primarily occurring in the direction above the disk and atomic or molecular out- flows mainly occurring diagonally). Still, most of these outflows will fall back to the disk, acting like a gas fountain. [ALMA (ESO/NAOJ/NRAO), T. Izumi et al.]