Lurking around at the center of every galaxy, the massive, or supermassive black holes are cosmic titans which can be millions or even billions of times more massive than the sun. That being said, it is obviously quite a task to determine the exact mass of a supermassive black hole.
In a new proof-of-concept observation, thanks to Atacama Large Millimeter/Submillimeter array or ALMA, astronomers have measured the mass of a supermassive black hole at the center of NGC 1097 which is a barred spiral galaxy which is nearly 45 million light-years away in the direction of the constellation Fornax. According to the researchers, the galaxy holds a black hole 140 million times more massive than our sun. Compared to that, the black hole at the center of the milky way is too light, being just a few million times heavier than our sun.
To achieve this result, the research team, led by Kyoko Onishi at SOKENDAI (The Graduate University for Advanced Studies) in Japan, precisely measured the distribution and motion of two molecules — hydrogen cyanide (HCN) and formylium (HCO+) — near the central region of the galaxy. The researchers then compared the ALMA observations to various mathematical models, each corresponding to a different mass of the supermassive black hole. The “best fit” for these observations corresponded to a black hole weighing in at about 140 million solar masses. The results are published in the Astrophysical Journal.
For making it possible, the research team led by Kyoko Onishi at SOKENDAI in Japan, measured the distribution and motion of two molecules near the center region of the galaxy- Hydrogen Cyanide (HCN) and Formylium (HCO+). Next, comparisons were done of the ALMA observations to various mathematical models, each corresponding to a different mass of the supermassive black hole. The best fit that the observations resulted in led the researchers to claim that the mass of the black hole could be 140 million solar masses. The results are published in Astrophysical Journal.
A similar technique was used previously with the CARMA telescope to measure the mass of the black hole at the center of the lenticular galaxy NGC 4526.
“While NGC 4526 is a lenticular galaxy, NGC 1097 is a barred spiral galaxy. Recent observation results indicate the relationship between supermassive black hole mass and host galaxy properties varies depending on the type of galaxies, which makes it more important to derive accurate supermassive black hole masses in various types of galaxies,” Onishi noted.
Currently, astronomers use several methods to derive the mass of a supermassive black hole; the technique used typically depends on the type of galaxy being observed.