P. Vosteen / NSF / AUI / NSF NRAO
Artist’s illustration of a rare trio of merging galaxies, J121/1219+1035, which is home to three supermassive, active, radio-emitting black holes, whose jets illuminate the surrounding gas.
Astronomers have identified a system of three active supermassive black holes that appear to be merging into a single system – a rare phenomenon that will help shed light on the physics behind complex mergers.
Three galaxies with supermassive black holes at their centers appear to be in the process of merging, giving rise to a single giant galaxy – something astronomers rarely observe.
To reach such colossal dimensions, it is believed that supermassive black holes sometimes have to devour or become massive during galactic collisions.
This process it is difficult to detectnot only because these mergers are fleeting compared to the lifetime of a black hole, but also because they are only easily observable emit light resulting from the active absorption of matterwhich is also rare. As a result, astronomers were only able to identify about 150 pairs of black holes galactics in full fusion.
In a new study, Emma Schwartzmana researcher at the US Naval Research Laboratory in Washington, and her team, have now discovered a group of three supermassive black holes, all activewhich appear to be unite into a single system.
The discovery of the triple galactic collision, which astronomers named J1218/1219+1035was presented in a recent publication in The Astrophysical Journal Letters.
“The more galaxies involved, the rarer the system“, explains Schwartzman, from the National Radio Astronomy Observatory (NRAO). “By observing that all three black holes in this system are radioluminous and actively emitting jets, we transform the concept of ‘triple active galactic nucleus‘ in reality.”
Each of these supermassive black holes is emitting low-frequency radiation in the form of radio wavescapable of passing through dust that blocks other types of light, which allowed Schwartzman and his team to observe them with two radio telescopesthe Very Long Baseline Array in Hawaii, and the Very Large Array in New Mexico, and exclude the hypothesis that the light comes from another sourcelike bright galaxies full of stars.
“What’s really fascinating is that all three of these black holes emit in the radio frequency range, something we had never observed“, says Schwartzman. “There is no guarantee that any black hole will emit in this range.”
Galaxy mergers are not rare in the Universe; in fact, they are thought to be one of the main mechanisms through which galaxies, and their respective supermassive black holes, grow. The Milky Way itself presents evidence of at least three or four major mergers throughout its 13 billion years of existence.
Astronomers have already cataloged a significant number of mergers between pairs of galaxies, but systems formed by three galaxies are much rarerexplains the , because these require the three galaxies to merge simultaneously, rather than a staggered process and hierarchical.
Second Isabella Lampertiresearcher at the University of Florence, in Italy, signs are already visible that galaxies began to interact with each otherbut are still in a relatively early phase of interactiongiven that two of the galaxies are still separated by around 70 thousand light years and the third is 300 thousand light years away.
However, compared to the total duration of their lives, which spans billions of years, “we are watching the outcome of this story. It’s like catch the final moments of a galactic soap opera“, he says to the astronomer Emma Onlyresearcher at Ruhr University Bochum, Germany.
Simulating the merger of three active supermassive black holes is extremely complex, Kun explains, but observing this system will allow physicists to better understand what happens in more intricate mergers. “This is the first step towards understand the physics of this type of system”, he concludes.
