Researchers at the Indian Institute of Astrophysics, Bengaluru, have observed that three supermassive black holes in three galaxies merge to form a triple active galactic nucleus, using data from India’s only space astronomy mission, Astrosat.
“Our study found that there are three galaxies, each with an active galactic nucleus that forms a triple AGN system. Cosmological modeling predicts that there should be 16% triple AGN, but only a handful have been observed so far, ”said Jyoti Yadav, lead author of the correspondence in the journal Astronomy and Astrophysics. To date, researchers have observed only five triple active galactic nuclei (AGNs).
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It is difficult to detect supermassive black holes as they do not emit light. However, black holes become bright when, when interacting with their environment, they swallow dust and gases, turning them into electromagnetic radiation.
Researchers suggest that merging galaxies are the ideal laboratories for detecting multiple supermassive black holes. “We generally expect all galaxies to have a black hole, but we don’t see it. But it can be observed by studying the interacting galaxies, when the gases move towards the central part of the galaxy and trigger the activity of the AGN. We expect multiple AGNs in interacting galaxy clusters, ”said Yadav.
Researchers were studying a pair of known galaxies, NGC7733 and NGC7734, when they detected an unusual bright cluster in the center of one of them. The groups, however, moved at a different speed compared to what was observed. The researchers said this meant that the group was not part of the same galaxy, but a small independent galaxy they named NGC7733N.
“Sometimes, when two galaxies are applied to each other, some of the matter can be removed from the galaxies. If this issue is enough, it can collapse under its own gravity and form a single small galaxy, ”said Yadav.
Researchers, including MIA’s Mousumi Das and Sudhanshu Barway, Francoise Combes of the College de France and Chaire Galaxies et Cosmologie-Paris, used data from Astrosat, which was released by the Space Research Organization of India. in 2015, the Infrared Survey Facility in South Africa and MUSE (Multi Unit Spectroscopic Explorer) spectroscopic data in Chile.
Yadav said that understanding the evolution of galaxies is necessary to understand the evolution of the universe. “Currently, we do not understand how gases reach the inner parsec (the parsec is a unit of length for measuring large distances to astronomical objects outside the solar system) of the galaxy region. AGNs also affect the evolution of galaxies; if we want to study the evolution of the universe we should know how galaxies evolve. An AGN sitting in the center of the galaxy can release large amounts of energy that can initiate star formation by pushing the gas or stopping it by removing gas from the galaxy, ”he said.