Astronomers from the Academy of Sciences and Moscow State University have found that the shape and size of galaxies in the distant past was determined by how many "embryos" of supermassive black holes contained their outskirts, according to an article published in the Journal of Cosmology and Astroparticle Physics.
“The black holes predicted by our model should have been present in the Universe in sufficient numbers to explain all the globular clusters that formed. It points to the existence of a sufficient number of black holes with a mass of several thousand Suns so that they can become the 'embryos' of globular clusters,”says Alexander Dolgov from the Institute for Theoretical and Experimental Physics of the Russian Academy of Sciences in Moscow, quoted by the press service of the Russian Science Foundation.
Most massive galaxies are believed to be inhabited by supermassive black holes, which can range from a million to billions of solar masses. The reasons for the formation of these objects are not yet entirely clear. Scientists initially believed that such objects arose in the same way as their normal "cousins" - as a result of the gravitational collapse of stars and the subsequent merger of several large black holes.
Observations of the first galaxies in the Universe made astrophysicists doubt this - it turned out that they were "inhabited" by black holes with a mass of tens of billions of Suns. Such objects simply would not have time to grow to this size if they were born small. Therefore, some scientists began to believe that supermassive black holes are born in more exotic scenarios - as a result of the collapse of giant clouds of "pure" atomic hydrogen or due to clumps of dark matter.
Today, most astronomers believe that black holes - "heavyweights" arose at the dawn of the universe from the so-called primordial black holes, which occupy an intermediate position between supermassive and ordinary black holes, whose origin is still unknown. Their mass, according to various estimates of scientists, was several tens or hundreds of thousands of solar masses. In the past ten years, astronomers have been actively looking for such "seeds" of black holes, and so far we know less than ten candidates for the role of such objects.
Dolgov and his colleague Konstantin Postnov of the State Astronomical Institute of Moscow State University have found that such "embryos" could play a key role in the formation of all galaxies, studying how often such black holes could have arisen even before the first clusters of stars erupted in the newborn universe.
Their calculations showed that in the first days of the life of the Universe, a huge number of such objects could appear, about 10-100 thousand times more than the number of all galaxies in the universe. This number of black holes, according to Postnov and Dolgov, should have been enough for the birth of all globular clusters known to us - the most ancient "families" of stars on the outskirts of galaxies, where all known black holes of intermediate mass were found.
These clusters of stars, in turn, are today considered to be a kind of "embryos" around which the nuclei of all spiral and elliptical galaxies known to us were formed in the distant past.
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A large number of such clusters in the early Universe prompted scientists to believe that the black holes living in them could "orchestrate" the growth of galaxies and control their shape and mass, and not vice versa, as many astrophysicists today believe.
Guided by this idea, scientists calculated how the shape of the galaxy changed with the change in the number of globular clusters and the mass of black holes in their centers, as well as with the increase and decrease in the mass of the "donut" of dark matter on the outskirts of galaxies, which is considered today the main driving factor of their birth … As it turned out, black holes played a decisive role in the birth of elliptical and spiral galaxies, forcing them to form even in cases where the ring of dark matter was absent.
A similar scenario for the formation of galaxies, as the researchers note, can explain one of the main cosmological mysteries - why the earliest galaxies have a very large mass and have very heavy black holes, whose existence scientists could not explain before.