ONISHI Shusuke / Graduate School of Science, The University of Tokyo,
Dept. of Space Astronomy and Astrophysics, ISAS
Today, it is believed that there is a supermassive black hole at the center of most galaxies. Many galaxies are observed to host "active galactic nuclei", which form the bright central region of the galaxy and shine due to gas accreting onto the central black hole. Studying these active galactic nuclei is important for understanding galaxy evolution because their huge energy radiation impacts the evolution of the host galaxy. The characteristics of the active galactic nucleus are believed to be affected by a doughnut-shaped gas structure surrounding the central black hole, which is known as the "molecular torus"; thus, understanding the inner structure of the molecular torus is essential to understanding both the active galactic nuclei and so the evolution of the galaxy. However, imaging the inner structure of the torus is difficult because the diameter of the torus is about 1/10,000th of that of the host galaxy.
In this research, we were able to probe the inner structure of the molecular torus in the active galactic nucleus of the galaxy IRAS 08572+3915 by making spectroscopic observations of the near-infrared absorption lines of the carbon monoxide molecules within the torus, rather than imaging the torus itself. As a result, it was found observationally that (1) the interior of the molecular torus is not composed of continuous gas but of discrete clouds of molecular gas, and forms a dynamic structure where these molecular clouds are inflowing or outflowing, and (2) the molecular clouds are dense gas with various temperatures ranging from approximately 30 to 700 K.
Read the full article here, "ISAS GATE"
[GATEWAY to Academic Articles: Inner structure of the doughnut-shaped molecular gas surrounding a black hole at the galactic center revealed with absorption lines of carbon monoxide]