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Morelia, Michoacán.- An international collaboration of astronomers and astronomers has revealed that supermassive black holes are so powerful that they affect not only their host galaxy but also neighboring galaxies. “The effect on neighboring galaxies is also contrary to what we expected,” said Dr. Vicente Rodríguez-Gómez, a researcher at the Institute of Radio Astronomy and Astrophysics (IRyA) of the UNAM Campus Morelia, and part of the research team.
Galaxies are large conglomerates of stars, gas, and cosmic dust. An example is the Milky Way, to which the Sun belongs. It is estimated that at the center of each galaxy there is a supermassive black hole whose gravitational field affects only a small region around the galactic center.
However, these black holes eject large amounts of radiation and matter that affect much of the host galaxy, heating interstellar gas and regulating star formation. This energy is expelled mainly in the direction of the minor axis of the host galaxy, as it is where it obtains less resistance.
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The new study, led by Dr. Ignacio Martín-Navarro, researcher at the Institute of Astrophysics of the Canary Islands, was recently published in the journal Nature. It combines observations and computer simulations to study how supermassive black holes affect the satellite galaxies around them, at even greater distances.
Usually, the hot gas around galaxies leads to a low rate of star formation in satellite galaxies, so satellite galaxies were expected to form stars at an even lower rate in the direction aligned with the lower axis of the central galaxy, due to all the energy injected by the supermassive black hole in that direction.
The research team analyzed the properties of galaxies belonging to thousands of groups and clusters, using observations from the Sloan Digital Sky Survey census. Surprisingly, they found that satellite galaxies form stars at a higher rate if they are aligned with the minor axis of the central galaxy, and at a lower rate if they are not aligned with the minor axis.
To explain this unexpected observational result, the scientific team proposed that the gas and matter that the hole expels “clears” the gas around the central galaxy, so that satellite galaxies continue their star formation without being interrupted.
In order to verify this conclusion, the team compared their observations to a cosmological simulation of the Universe called Illustris-TNG, which in its code implements a particular treatment for the interaction between supermassive black holes and their host galaxies.
“Consistent with the observations, the simulation shows a clear variation in the star formation activity of satellite galaxies depending on their position relative to the central galaxy,” said Dr. Rodríguez-Gómez.
This result gives observational support to the idea that supermassive black holes play an important role in regulating the evolution of galaxies, a fundamental pillar in current knowledge of the Universe. Previously it had been very difficult to measure the possible effect of black holes on real galaxies, beyond theoretical considerations.
“This work has been possible with the collaboration between two communities, the observational and the theoretical that, in the field of extragalactic astrophysics, are finding in cosmological simulations a very useful tool to understand how the Universe behaves, “said Dr. Martín-Navarro.
