Japanese researchers have found a mysterious second largest black hole in the Milky Way, which could be possible missing link in black hole evolution. Tomoharu Oka and his team of astronomers from Keio University in Japan found the enigmatic gas cloud, called CO-0.40-0.22, about 200 light years away from the center of the Milky Way.
The CO-0.40-0.22 is unusual with a surprisingly wide velocity dispersion of the cloud containing gas with a very wide range of speeds. The team found the black hole using the Nobeyama 45-m radio telescope in Japan and the ASTE radio telescope in Chile, both operated by the National Astronomical Observatory of Japan.
To team then used the Nobeyama 45-m Telescope to obtain 21 emission lines from 18 molecules and the results showed that the cloud has an elliptical shape with a compact but low density component with a very wide velocity dispersion of 100 km/s, and another dense component extending 10 light years with a narrow velocity dispersion.
There no holes inside the cloud, indicating that the velocity dispersion is not caused by indegenous energy such as supernova explosions. When the performed a simple simulation of gas clouds flung by a strong gravity source, the gas clouds are first attracted by the source and their speeds increase as they approach it, reaching maximum at the closest point to the object.
After that the clouds continue past the object and their speeds decrease.
The team found that a model using a gravity source with 100 thousand times the mass of the Sun inside an area with a radius of 0.3 light years provided the best fit to the observed data.
“Considering the fact that no compact objects are seen in X-ray or infrared observations,” said Prof. Oka, the lead author of the paper that was published in the Astrophysical Journal Letters. “As far as we know, the best candidate for the compact massive object is a black hole,” he added.
Going by the team’s assertion, this will be the first detection of an intermediate mass black hole. If the cloud CO-0.40-0.22, located only 200 light years away from Sgr A* (the 400 million solar mass SMBH at the center of the Milky Way), contains an intermediate mass black hole, it might support the intermediate mass black hole merger scenario of SMBH evolution, said researchers throwing an interesting angle to the evolution of black holes.
These results also open a new way to look for black holes with radio telescopes. “Investigations of gas motion with radio telescopes may provide a complementary way to search for dark black holes” said Oka, who is confident that similar observations will increase the potential to find more such black hole candidates dramatically.”