In a new proof-of-concept observation, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have measured the mass of the supermassive black hole at the center of NGC 1097 — a barred spiral galaxy located approximately 45 million light-years away in the direction of the constellation Fornax. The researchers determined that this galaxy harbors a black hole 140 million times more massive than our Sun. In comparison, the black hole at the center of the Milky Way is a lightweight, with a mass of just a few million times that of 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.
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 vary depending on the type of galaxies, which makes it more important to derive accurate supermassive black hole masses in various types of galaxies,” Onishi said.
