The process by which dark matter transforms supermassive black holes into high-energy quasars has occurred throughout history, influencing the past evolution of the universe. There is a supermassive black hole at the center of every galaxy. After exceeding a certain size, these black holes become active, emit large amounts of radiation, and are called quasars. It is thought that the activation of these quasars is due to the presence of massive dark matter haloes (DMH) around galaxies, which draw matter towards the center of the galaxy and provide energy for the black hole.
A research team from the University of Tokyo has discovered that quasars, influenced by the surrounding dark matter halo, have consistent activation patterns throughout the history of the universe. This research provides new insights into the formation and growth of black holes and the broader evolution of the universe.
A team of researchers including scientists from the University of Tokyo has surveyed hundreds of ancient quasars for the first time and found that this behavior is remarkably consistent throughout history. This is surprising because many large-scale processes change throughout the life of the universe, so the activation mechanisms of quasars may have implications for the evolution of the entire universe.
Measuring dark matter halos
Measuring the mass of a dark matter halo is not easy; it is a notoriously elusive substance, and the word "matter" is not an overstatement to describe it, because dark matter's actual properties are not yet known. We only know it exists because of its gravitational influence on large structures like galaxies. Therefore, dark matter can only be measured by looking at its gravitational influence on things. This includes the way dark matter pulls on or affects the motion of objects, or the lensing effect (bending of light) of objects behind a dark matter-like region.
This challenge becomes even greater at greater distances, because the light from more distant, older phenomena can be very faint. But that hasn’t stopped Professor Nobuge Kashiwagawa of the Department of Astronomy and his team from trying to answer a long-standing question in astronomy: How are black holes born and how do they grow?
Researchers are particularly keen to explore questions related to supermassive black holes, the largest kind of black holes that exist at the center of every galaxy. Studying them would be very difficult if it weren't for the fact that some supermassive black holes are so massive that they start ejecting extremely powerful jets of material or balls of radiation, in both cases becoming what we call quasars. These quasars are so powerful that we can now observe them with modern technology, even from great distances.
Research results and significance
Baichuan said: "We measured for the first time the typical mass of the dark matter halo surrounding active black holes in the universe about 13 billion years ago. We found that the DMH mass of quasars is very stable, about 10 trillion times the mass of the sun. We have already measured the newer mass around quasars. The DMH made measurements that are strikingly similar to what we see from older quasars, which is interesting because it shows that there is a characteristic DMH mass that seems to activate quasars, whether it happened billions of years ago or now."
Far away quasars appear faint because the light that left them long ago has spread out, been absorbed by the intervening material, and stretched into nearly invisible infrared wavelengths by the long-term expansion of the universe. Therefore, Hashikawa and his team began surveying the sky in 2016 using a variety of different instruments, the most important of which is the Japanese Subaru Telescope in Hawaii, USA.
Kashiwakawa said: "The upgraded Subaru telescope can see further than before, but we can learn more by expanding international observation projects. The Vera-C-Rubin Observatory in the United States and even the European Union's space Euclid satellite launched this year will scan a larger range of the sky and discover more DMHs around quasars. We can more fully understand the relationship between galaxies and supermassive black holes. This may help us understand how black holes form and grow."