Two black holes grow together in a close galactic merger

The two supermassive black holes are only 750 light-years apart from each other.


Two simultaneously growing supermassive black holes have been discovered near the center of a newly merged galaxy using the Atacama Large Millimeter/submillimeter Array ( ALMA ).

These supermassive giants are the closest to each other that scientists have ever observed at multiple wavelengths. What’s more, the new research reveals that binary black holes and the galaxy mergers that create them may be surprisingly frequent in the Universe. Results of the new research have been published in The Astrophysical Journal Letters , and presented at the 241st meeting of the American Astronomical Society (AAS) in Seattle, Washington.

a distant event

Just 500 million light-years from Earth, in the constellation Cancer, UGC4211 is an ideal candidate for studying the final stages of galaxy mergers, which occur more frequently in the distant Universe and, as a result, can be difficult to observe. When scientists used ALMA ‘s high-sensitivity 1.3mm receivers to take a deep look at the active galactic nuclei of the merger—compact, highly luminous areas of galaxies caused by the accretion of matter around central black holes —they found not one, but two black holesgluttonously devouring the by-products of the merger. Amazingly, they were eating side by side, with only 750 light-years between them.

“The simulations suggested that most of the population of binary black holes in nearby galaxies would be quiescent, because they are more common, and not two growing black holes like we have found,” Michael Koss, senior research scientist, said in a statement. of Eureka Scientific and lead author of the new research.

Koss added that the use of ALMA is a game changer, and that finding two black holes so close together in the near Universe could pave the way for further study of this exciting phenomenon. ” ALMA is unique in that it can see through large plumes of gas and dust and achieve very high spatial resolution to see things very close. Our study has identified one of the closest pairs of black holes in a merger of galaxies, and since we know that galaxy mergers are much more common in the distant Universe, these black hole binaries may also be much more common than previously thought.”

If paired black hole binary pairs are indeed common, as Koss and his team postulate, there could be significant implications for future gravitational wave detections.

Ezequiel Treister, an astronomer at the Catholic University of Chile and co-author of the research, says: “There could be many pairs of growing supermassive black holes in the centers of galaxies that we have not been able to identify until now. If this is the case , in the near future we will observe frequent gravitational wave events caused by the mergers of these objects throughout the Universe.”

Combining the ALMA data with multi-wavelength observations from other powerful telescopes such as Chandra, Hubble, ESO’s Very Large Telescope and Keck added fine detail to an already compelling story.

“Each wavelength tells a different part of the story. While ground-based optical images showed us the entire merging galaxy, Hubble showed us the nuclear regions in high resolution. X-ray observations revealed that there was at least one nucleus active galactic in the system,” Treister said. “And ALMA showed us the exact location of these two growing and hungry supermassive black holes. All this data together has given us a clearer picture of how galaxies like ours turned out to be the way they are and what they will become in the future” .

A new field of study

Until now, scientists have mainly studied only the early stages of galaxy mergers. The new research could have a profound impact on our understanding of the impending merger of the Milky Way with the nearby Andromeda Galaxy.

Koss said: “The collision of the Milky Way and Andromeda is in its early stages and is predicted to occur in about 4.5 billion years. What we have just studied is a source in the final stage of the collision, so we What we’re seeing foreshadows that merger and also gives us insight into the connection between the merger and the growth of black holes and eventually the production of gravitational waves.” (Europe Press)