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Astronomers from Japan, Taiwan and Princeton University discovered 83 quasars powered by supermassive black holes in the distant universe, at a time when it was less than 10% of its current age .
"It is remarkable that such dense, massive objects could have formed so soon after the Big Bang," said Michael Strauss, professor of astrophysics at Princeton University, one of the world's leading physicists. -authors of the study. "Understanding how black holes can form in the primitive universe and how common they are is a challenge for our cosmological models."
This discovery greatly increases the number of black holes known at this time and reveals, for the first time, how common they are at the beginning of the history of the universe. In addition, it provides new information on the effect of black holes on the physical state of gas in the early universe during its first billion years. The research appears in a series of five articles published in The astrophysical journal and the Publications of the Astronomical Observatory of Japan.
The supermassive black holes, located in the center of the galaxies, can be millions, even billions of times more massive than the sun. Although they are widespread today, it is unclear when they were formed and how many existed in the distant early universe. A supermassive black hole becomes visible when the gas accumulates on it, making it shine like a "quasar". Previous studies were sensitive only to the rarest, brightest quasars, and therefore to the most massive black holes. The new discoveries explore the population of weaker quasars, powered by black holes of a mass comparable to most black holes observed in the current universe.
The research team used data obtained with a state-of-the-art instrument, "Hyper Suprime-Cam" (HSC), mounted on the Subaru telescope of Japan's National Observatory of Astronomy, located on the summit of Maunakea in Hawaii. HSC has a gigantic field of vision – 1.77 degrees, or seven times the surface of the full moon – mounted on one of the world's largest telescopes. The HSC team studies the sky during 300 nights of use of the telescope, spread over five years.
The team selected distant quasar candidates from sensitive HSC survey data. They then conducted an intensive observation campaign to obtain the spectra of these candidates, using three telescopes: the Subaru telescope; the Gran Telescopio Canarias on the island of La Palma in the Canary Islands, Spain; and the southern Gemini telescope in Chile. The investigation revealed 83 very distant quasars hitherto unknown. With 17 quasars already known in the survey area, the researchers discovered that there was about a supermassive black hole per giga-light-year cube, that is, if you divide the imaginary cubes representing a billion light-years on one side, each containing a supermassive black hole.
The quasars sample of this study is about 13 billion light years from Earth; in other words, we see them as they existed 13 billion years ago. While the Big Bang took place 13.8 billion years ago, we look back and see these quasars and these supermassive black holes appeared about 800 million years after the creation of the 39, universe (known).
It is widely accepted that hydrogen in the universe was once neutral, but was "re-ionized" – divided into its protons and electrons – at the time of the birth of the first generation of "hydrogenation". stars, galaxies and supermassive black holes. a few hundred million years after the Big Bang. This is an important step in cosmic history, but astronomers still do not know what has provided the incredible amount of energy required to cause reionization. A convincing hypothesis suggests that there were many more quasars in the primitive universe than those previously detected, and that it was their integrated radiation that re-ionized the universe.
"However, the number of quasars we have observed shows that this is not the case," explained Robert Lupton, a Ph.D. from Princeton in 1985. Former student, principal investigator in astrophysical sciences. "The number of quasars seen is well below the number needed to explain reionization." The reionization was therefore caused by another source of energy, probably many galaxies that began to form in the young universe.
This study was made possible by the investigative capacity of Subaru and HSC, a world leader. "The quasars we have uncovered will be an interesting topic for further observations on current and future installations," said Yoshiki Matsuoka, a former Princeton postdoctoral researcher, today at Ehime University of Japan, who directed the study. "We will also study the formation and early evolution of supermassive black holes by comparing measured number density and luminance distribution with theoretical model predictions."
Based on the results so far, the team is eager to find more distant black holes and discover when the first supermassive black hole appeared in the universe.
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