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Using the James Webb Space Telescope, astronomers have looked back 13 billion years to discover surprisingly lonely, supermassive, black hole-powered quasars.
The observations from the James Webb Space Telescope (JWST) are confusing because isolated black holes should struggle to accumulate enough mass to reach supermassive status, especially just a few hundred million years after the Big Bang. The discovery further muddies the waters when it comes to the puzzle of how some black holes grew to masses equivalent to millions or even billions of suns when the universe was less than a billion years old.
The findings came after a team of scientists used the JWST to study the environments of five of the earliest known quasars, which formed when the cosmos was between 600 and 700 million years old. The team found that the environment of these quasars, known as ‘quasar fields’, was surprisingly varied. Some of these were the densely packed environments that scientists predict, but others were sparsely populated “empty stores” that would struggle to fuel the growth of supermassive black holes.
‘Contrary to previous thinking, we find that on average these quasars are not necessarily in the highest density regions of the early Universe. Some appear to be in the middle of nowhere,” Anna-Christina Eilers, assistant professor of physics at the Massachusetts Institute of Technology, said in a statement. “It’s hard to explain how these quasars can grow so big when they don’t seem to have anything to feed on.”
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Quasars require full pantries
Supermassive black holes are believed to lurk at the hearts of all major galaxies in the relatively modern universe. Because no star is big enough to collapse and because black holes have such monstrous masses, scientists know that supermassive black holes must form in different ways than so-called “mass black holes,” with masses between 10 and 100 times that of the sun. by the death of massive stars.
Supermassive black holes can grow through progressive mergers of increasingly larger black holes, models suggest. The problem, however, is that this process should last more than 1 billion years. Yet the JWST sees supermassive black holes that formed in much less time.
It is possible to see these supermassive black holes because they reside in a turbulent, gas-rich immediate environment called active galactic nuclei (AGN) from which they feed. That also facilitates their growth. The immense mass of the black holes in these environments causes oblate clouds of gas and dust to glow brightly around them, often outshining the combined light of every star in the galaxy in which they reside. This light, trillions of times brighter than the sun, indicates a quasar.
However, supermassive black holes require a ‘delivery service’ to keep their immediate surroundings well-filled with gas and dust to achieve this incredible brightness.
“It’s simply phenomenal that we now have a telescope that can capture the light from 13 billion years ago in so much detail,” says Eilers. “For the first time, JWST allowed us to look at the environment of these quasars, where they grew up and what their neighborhoods looked like.”
To investigate the wider environment of quasars, the team selected five supermassive black hole-powered regions studied by the JWST between August 2022 and June 2023. This required multiple images “merged” to create a quasar field mosaic for each supermassive black hole neighborhood.
By incorporating the different wavelengths of light into the images, it was also possible to determine whether the light came from a quasar’s neighboring galaxy and measure how far away that galaxy originated from the bright central quasar.
“We found that the only difference between these five quasars is that their environments look so different,” Eilers said. ‘For example, one quasar has almost fifty galaxies around it, while another has only two. And both quasars are within the same size, volume, brightness and time of the universe.
“That was really surprising to see.”
Related: The ancient supermassive black hole blows a galaxy-killing wind, James Webb Space Telescope finds
Did early supermassive black holes have ‘growth spurts’?
The team’s findings challenge the idea of the growth of supermassive black holes and even the formation of galaxies as a whole. The current understanding is that this evolution was guided by a vast ‘cosmic web’ of dark matter; dark matter accounts for about 85% of all matter, but remains essentially invisible to us.
Filaments of dark matter in the cosmic web channeled gas and dust into the early universe, attracting primordial matter along its vast tendrils. Where the strands of this cosmic web met, too-dense regions of matter gathered. This is where early galaxies were built and where the first quasars should be found.
“The cosmic web of dark matter is a solid prediction of our cosmological model of the universe, and can be described in detail using numerical simulations,” team leader Elia Pizzati, a graduate student at Leiden University, said in the statement. “By comparing our observations with these simulations, we can determine where in the cosmic web quasars are located.”
The supermassive black holes located at these nodes in the cosmic web would have to grow via the steady and rapid accretion of gas and dust brought in by the cosmic web as a galactic Grub Hub – this would give the quasars monstrous masses and extreme brightness can achieve – but scientists still need to know how this happened so early in the history of the universe.
“The main question we’re trying to answer is: How do these billion-solar-mass black holes form at a time when the universe is still very, very young? It’s still in its infancy,” Eilers says.
Unfortunately, this research appears to have raised more questions than answering those already troubling scientists. The barren neighborhoods appear to indicate a lack of dark matter and an excessive density of cosmic web nodes. If that is the case, current theories of growth mechanisms cannot explain these quasars.
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One possible solution to this mystery is that these early quasars are actually surrounded by cosmic dust and are therefore not visible. The team now plans to ‘tune’ their observations of these potentially empty quasar fields to discover such cloaked galaxies.
“Our results show that there is still a significant piece of the puzzle missing about how these supermassive black holes grow,” Eilers concluded. “If there isn’t enough material around for some quasars to grow continuously, that means there must be some other way for them to grow, which we have yet to figure out.”
The team’s research was published October 17 in The Astrophysical Journal