September 5, 2017
Keio University
A research team led by Professor Tomoharu Oka of the Department of Physics, Faculty of Science and Technology, Keio University, has conducted detailed radio observations of the peculiar molecular cloud CO–0.40–0.22, discovered near the center of the Milky Way Galaxy, using the Atacama Large Millimeter/submillimeter Array (ALMA).
This peculiar molecular cloud is located about 200 light-years away from Sagittarius A* (Sgr A*), the nucleus of the Milky Way Galaxy. Its unusually wide velocity dispersion had suggested the possibility that a black hole with a mass of 100,000 solar masses was lurking inside. As a result of the observations, a compact, high-density molecular cloud and a point-like radio source, CO–0.40–0.22*, were detected near the center of the peculiar molecular cloud CO–0.40–0.22. The detected point-like radio source has a brightness of 1/500th that of Sgr A* and exhibits a spectrum clearly different from thermal radiation from plasma or interstellar dust. A gravitational N-body simulation, placing a point-like gravitational source of 100,000 solar masses at the position of CO–0.40–0.22*, was found to reproduce the distribution and motion of the surrounding gas very well. These findings suggest that the point-like radio source CO–0.40–0.22* is the black hole itself, whose existence had been suggested within the peculiar molecular cloud CO–0.40–0.22. This is the first case in which the entity of an "intermediate-mass black hole" candidate has been confirmed in our own Milky Way Galaxy.
The results of this research were published in the British scientific journal "Nature Astronomy" on September 4.
For the full press release, please see below.