There were surprisingly massive black holes even in the early Universe. But where they got the “food” from to grow so quickly remained a mystery. Now an astronomical discovery provides an answer. Researchers have discovered a supermassive black hole closely surrounded by six galaxies embedded in gas filaments. This ensemble is 300 times the volume of the Milky Way and existed when the universe was only 0.9 billion years old. The presence of so much matter around the black hole could have provided it with the nourishment it needed to grow rapidly.
In recent years, astronomers have discovered several dozen distant galaxies with highly active and massive black holes that must have formed within the first billion years after the Big Bang. As so-called quasars, these active galaxy nuclei emit so much light that they are visible despite the enormous distances. Many of the supermassive black holes in the center of these galaxies combine several billion solar masses and shine brighter than trillion suns. This raises the question of how these gravitational giants were able to grow so rapidly in the relatively short time after the Big Bang and the formation of the first stars. Because in order to gain mass, the black holes have to absorb larger amounts of matter. Astronomers also suspect that several smaller predecessor holes have also merged into one larger one. But the nourishment necessary for these objects was still rather rare in the early days of the universe.
Cosmic spider web
“These are extreme systems for the existence of which we have not yet had a good explanation,” says lead author Marco Mignoli from the National Institute for Astrophysics (INAF) in Bologna. To gain more information, he and his team studied several early quasars with the most powerful optical telescopes currently available, including the Very Large Telescope at the European Southern Observatory in Chile. They found what they were looking for with the Quasar SDSS J1030 + 0524. This supermassive, active black hole comprises around one billion solar masses and existed 0.9 billion years after the Big Bang. However, the observations revealed that this gravity giant was not floating in space alone: it is surrounded by six galaxies that are embedded in a kind of cosmic spider web made of gas. “The filaments of the cosmic web are like spider web threads,” explains Mignoli. “The galaxies lie and grow where the filaments cross.”
For the first time, such a tight cluster was observed from as soon after the Big Bang as the astronomers explain. Together this structure extends over 300 times the volume of the Milky Way. The supermassive black hole is also integrated into the network of gas and star clusters. For four of the six galaxies, the researchers were able to prove a direct connection to the black hole. “Gas streams can flow along the filaments, which are available as food to both the galaxies and the central supermassive black hole,” explains Mignoli. As he and his colleagues discovered, the “spider web” and the galaxies in it contain enough gas to provide the “food” for the central black hole so that it could quickly become a supermassive giant.
Food for the rapid growth of the first black holes
According to astronomers, the discovery of this cosmic spider web could explain where the first large black holes got their food from. “Our studies have contributed an important part to the largely incomplete puzzle that describes the formation and growth of such extreme, but relatively common objects so quickly after the Big Bang,” says Mignoli’s colleague Roberto Gilli. The observations support the assumption that black holes grew up inside large, network-like structures with a high proportion of gas. According to one theory, such cosmic galaxy clusters formed because there were huge zones with a high density of dark matter in the early cosmos. These dark matter halos attracted large amounts of gas, which became a dense network of cosmic gas filaments. At the junctions of these filaments, intense star formation resulted in galaxies and black holes.
“Our results support the idea that the most distant and massive black holes arise and grow in massive halos of dark matter in large-scale structures,” says co-author Colin Norman of Johns Hopkins University in Baltimore. He attributes the fact that such “spider webs” had not been seen earlier to the limitations of the observation technology – the light intensity and resolution of the telescopes were simply not sufficient. However, because this is increasingly changing, astronomers assume that they will be able to discover even more such structures in the future. “We think we’ve just seen the tip of the iceberg and that the few galaxies that have been discovered around this supermassive black hole are only the brightest,” explains co-author Barbara Balmaverde of the Turin Astrophysical Observatory.
Source: Marco Mignoli (National Institute for Astrophysics (INAF), Bologna) et al., Astronomy & Astrophysics, doi: 10.1051 / 0004-6361 / 202039045