First Detection of an Intermediate-Mass Black Hole Candidate in the Milky Way
September 27, 2017 Keio University
Professor Tomoharu Oka of the Department of Physics, Faculty of Science and Technology, Keio University and his research team carried out a detailed radio wave observations using the Atacama Large Millimeter/submillimeter Array (ALMA; ALMA telescope) on the peculiar molecular cloud CO–0.40–0.22, which was discovered in the central region of the Milky Way. This peculiar molecular cloud lies about 200 light-years away from Sagittarius A* (star), the nucleus of the Milky Way, and inside it’s unusually broad velocity width, the researchers identified the possibility of an intermediate-mass black hole with a mass 100,000 times greater than the sun. From the observations, a point-like radio source CO–0.40–0.22* (star), as well as a highly dense and compact molecular cloud near the center of CO–0.40–0.22, were detected. The luminosity of the detected point-like radio source is 1/500 of Sagittarius A*, and it has a radiation spectrum that is distinctly different from that of thermal plasma or interstellar dust. Results of gravitational N-body simulations that placed a 100,000-solar mass point-like mass at the location of CO–0.40–0.22* showed that the distribution and motion of gas in the adjacent area could be reproduced very well. From these findings, it can be thought that the point-like radio source CO–0.40–0.22* is the intermediate-mass black hole that has been suggested to exist within the peculiar molecular cloud CO–0.40–0.22. This is the first detection of an intermediate-mass black hole candidate within the Milky Way galaxy in which we exist.
The results of this research were published in the September 4 issue of the British scientific journal Nature Astronomy.