A state-of-the-art VLT instrument has made the first direct measurement of the mass of a distant supermassive black hole whose light has been reaching us for 11 billion years. It turned out to be four times “lighter” than it should be based on the mass of the galaxy in which it is located. In the immediate Universe, there is a natural relationship between the general properties of galaxies and the mass of the supermassive black hole at their center. From this, scientists conclude that galaxies appear to be evolving together with a central black hole. At the same time, much depends on the most active stage of its development, when the hole is in the quasar stage. During the quasar phase, the radiation from the absorbed material is so strong that it affects star formation within the galaxy (the radiation “blows away” the gas, suppressing the formation of new stars). Astronomers are interested in how those interactions change over time. Fortunately, these objects are so bright that they can be seen from billions of light years away. And now researchers have a tool to help them see in more detail what’s happening in the immediate vicinity of black holes: an improved GRAVITY at his VLT telescope facility at the European Southern Observatory. Ta. A team led by Taro Shimizu from the Max Planck Institute for Extraterrestrial Physics used GRAVITY+ to study the supermassive black hole J0920 (SDSS J092034.17+065718.0) at redshift z = 2.3. Light from our surroundings travels to us for about 11 billion years.
To directly measure a black hole’s mass, astronomers track the movement of surrounding gas and stars. The faster this movement, the greater the mass. The problem is that this movement is very difficult to detect over long distances. GRAVITY+’s adaptive optics offers exactly this possibility. This instrument combines data from four VLT 8-meter telescopes. In terms of accuracy, the 120 meter telescope “pays off”. The research team was able to detect the movement of gas clouds in the dense disk surrounding J0920. To calculate the actual size of the central region around a quasar, they need to know its geometry, so the scientists compared the resulting data with computer models. This allowed us to directly measure the mass of such a distant black hole for the first time. The mass of the object was 320 million solar masses, while the mass of the galaxy was found to be about 60 billion solar masses. The mass of the black hole was found to be about a quarter of that of modern galaxies. This means that, at least in some galaxies, there is a lag between the growth of the galaxy itself and the growth of the black hole. The researchers’ study was published in the journal Nature.