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Astronomers have struggled to understand the emergence of supermassive black holes in the early universe since the discovery of these objects at distances dating back only 750 million years after the Big Bang. Understanding how supermassive black holes form and grow in the early universe has become a major challenge. Theories and computer simulations predict the rapid growth of black holes in the first dusty star-forming galaxies, but until now they had not been observed. Recently, in archival data from NASA / ESA Hubble Space Telescope and other space and earth observatories, astronomers discovered a unique object in the distant and early universe. That would be the missing link between star-forming galaxies and the emergence of quasars – supermassive black holes that collect large amounts of gas.
The quasar, which formed very early in the universe, is brighter than thousands of galaxies. It emits a titanic energy in the form of a beam over millions upon billions of kilometers. However, its size only corresponds to a few solar systems (ours) placed side by side.
It was in 1963 that Maarten Schmidt, a Dutch astronomer, identified and measured the distance to a quasar. Using large telescopes, about 130,000 quasars have been observed. This made it possible to suggest that their center contains a supermassive black hole that represents almost its entire mass: from several million to a few billion times the mass of the Sun. Fabric near the black hole revolves around it at high speed and forms a growth disk. This swirling disk of matter and gas generates through friction an enormous amount of heat. A part approaches, as it accelerates, the horizon of the black hole that catches it. Since nothing escapes from the latter, it is the material of the disc that is responsible for the light emission. It is in its heart that the quasar therefore derives its energy and its power.
Thus, quasars, driven by matter falling into their supermassive black hole, would have formed early in the history of the universe, only 700 to 800 million years after the Big Bang. Scientists believe they evolved from supermassive black holes in dusty galaxies, a class of galaxies that have also been confirmed to appear early. But until now, there was no direct evidence linking the two and helping to understand how supermassive black holes form and grow in the early universe.
This is done with this discovery in the Hubble archive images, among which astronomers have reported on a specific object named GNz7q. It would be the first fast-growing black hole discovered in the early universe, and therefore ” missing joints of their origin. The study is published in Nature.
A super massive black hole for everyone to see
Scientists have found evidence of the missing link by analyzing archived Hubble Space Telescope data for an area in the sky known as the Hubble GOODS North Field in the constellation Ursa Major. This field has been thoroughly studied by Hubble and other telescopes.
The team noticed an object called GNz7q, which appears to be a black hole that has just begun to dominate its host galaxy and becomes a quasar. Additional archival data, including the Subaru telescope, which can look further into infrared wavelengths than Hubble, has allowed astronomers to distinguish the black hole from its host galaxy. Studying the compact ultraviolet emissions from the black hole accretion disk helped them determine that GNz7q had existed for only 750 million years after the Big Bang.
Gabriel Brammer, astronomer at the Niels Bohr Institute at the University of Copenhagen and co-author of the study, said in a statement: GNz7q is a unique find right in the center of a famous and well-studied skyfield. It is unlikely that the discovery of GNz7q in the relatively small GOODS-North study area was a game of chance, but rather that the prevalence of such sources is actually much higher than assumed. “.
In other words, there may be many more randomly overlooked, forming black holes waiting to be discovered. GNz7q could also help scientists perform an even more important task: to elucidate the origin of supermassive black holes.
Missing joints, the key to the origin of supermassive black holes
As mentioned above, scientists believe that supermassive black holes originate from the dusty nuclei of star-forming galaxies, that is, galaxies that produce stars very rapidly. Then, by consuming all the dust and gas from these galaxies, the black hole probably gets very hot and eventually appears as an extremely luminous quasar or supermassive black hole. All these steps produce very specific emission spectra according to the simulations, spectra that we can therefore try to detect, associated with very old galaxies.
Seiji Fujimoto, astronomer at the Niels Bohr Institute at the University of Copenhagen and lead author of the paper, explains: Our analysis suggests that GNz7q is the earliest example of a rapidly growing black hole in the dusty core of a star-forming galaxy at a time close to the oldest known supermassive black hole in the universe. The properties of the object across the electromagnetic spectrum are in excellent agreement with predictions from theoretical simulations “.
In fact, the host galaxy GNz7q forms stars at a rate of 1600 solar masses of stars per year, and GNz7q itself appears bright at ultraviolet wavelengths, but very faint at X-ray wavelengths. , its redness on the GOODS-North study is probably the product of quasar candles that turn red from dust from combustion. The team interpreted this to suggest that GNz7q actually contains a fast-growing black hole. Specifically, these results suggest that the nucleus of the accretion disk from which the x-rays originate is still hidden; while the outer part of the accretion disk, where the UV light comes from, disappears. He adds: ” GNz7q establishes a direct link between these two rare populations and offers a new way of understanding the rapid growth of supermassive black holes at the beginning of the universe. “.
Rediscover the sky with the James Webb Telescope
Finding GNz7q hidden in plain sight was only possible because of the unique and detailed multi-wavelength datasets available for GOODS-North. Without this wealth of data, GNz7q would have been easy to overlook as it lacked the characteristics commonly used to identify quasars in the early universe. The team now hopes to systematically search for similar objects using dedicated high-resolution studies and utilize spectroscopic instruments from NASA’s James Webb Space Telescope to study objects such as GNz7q in unprecedented detail.
Fujimoto concludes: Complete characterization of these objects and study of their evolution and underlying physics in much greater detail will be possible with the James Webb Space Telescope. Once in normal operation, Webb will have the power to determine the true frequency of these fast-growing black holes. “.
In conclusion, these data associated with the commissioning of the James-Webb Telescope will therefore allow us to better understand how the Milky Way and its supermassive black hole were formed and evolved.