New Delhi | Jagran Trending Desk: In a proud moment for the whole country, Indian researchers have discovered three supermassive black holes from as many galaxies that are merging to become a triple active galactic nucleus, said the Department of Science and Technology.

A triple active galactic nucleus refers to the compact region at the centre of a newly discovered galaxy that is capable of having much higher-than-normal luminosity.

As per the information provided by the Department of Science and Technology, this is a very rare occurrence that has taken place in our nearby galaxies and it specifies that small merging groups are exemplary laboratories that will help in detecting the multiple accreting supermassive black holes and increases the possibility of detecting such rare occurrences.

These supermassive black holes are hard to find as they do not emit any light. However, they can show their presence by interacting with their surroundings. The time when dust and gas drops from the surroundings fall onto a supermassive black hole, some of the mass is swallowed by the black hole whereas little of it is transformed into energy and emitted as electromagnetic radiation that makes the black hole appear very luminous.

These are referred to as active galactic nuclei (AGN) and release huge amounts of ionized particles and energy into the galaxy and its surroundings. Both of them play an essential role in the contribution of the growth of the medium around the galaxy and ultimately the evolution of the galaxy itself.

A team of researchers from the Indian Institute of Astrophysics consisting of Jyoti Yadav, Mousumi Das, and Sudhanshu Barway along with Francoise Combes of College de France, Chaire Galaxies et Cosmologie, Paris, while learning a known interacting galaxy pair, NGC7733, and NGC7734, found that unusual emissions from the centre of NGC7734 and a large, bright clump along the northern arm of NGC7733.

According to their inspection, the clump is moving at a different velocity compared to the galaxy NGC7733 itself. The scientist mentioned that this clump was not a part of NGC7733; rather, it was an entire tiny separate galaxy that was behind the army. They named this galaxy NGC7733N.

The results were published in a journal named Astronomy and Astrophysics used data from the Ultra-Violet Imaging Telescope (UVIT) onboard the first Indian space observatory ASTROSAT, the European integral field optical telescope called MUSE mounted on the Very Large Telescope (VLT) in Chile and infrared images from the optical telescope (IRSF) in South Africa.

Meanwhile, the images obtained from the UC and H-alpha also supported the presence of the third galaxy by disclosing star formation along with the tidal tails, which could be a result of the merger of NGC7733N with the larger galaxy. All these galaxies host an active supermassive black hole in their nucleus and hence form a very rare triple AGN system, as per the statement released by the ministry.

The research suggests that one of the main factors which are impacting galaxy evolution in galaxy interactions. This thing happens when galaxies proceed close to each other and make a great gravitational force on each other. During this process, the respective supermassive black holes can get near each other. The dual black holes start consuming gas from their surroundings and become dual AGN.

According to the explanation given by IIA, if two galaxies crash together, their black hole will also come closer by transferring the kinetic energy to the surrounding gas. There is a reduction in distances between the blackholes with time until the separation is around a parsec (3.26 light-years).

The two black holes are then unable to lose any further kinetic energy to get even closer and merge. This refers to the final parsec problem. However, the existence of a third black hole can help in solving the problem. The dual merging blackholes can transfer their energy to the third blackhole and merge.

Earlier, several AGN pairs have been detected however the triple  AGN are extremely rare and only a few were found through the help of X-ray observations. But the IIA team expects such triple AGN systems to be more common in small merging groups of galaxies. Although the main focus of the study is on one system, results advised that small merging groups are ideal laboratories to detect multiple supermassive black holes.

(With PTI inputs)

Posted By: Mallika Mehzabeen