New data confirm that the titanic collisions of galaxies ignite the most powerful active galactic nuclei.
Active galactic nuclei (AGN) are phases in which supermassive black holes at the centre of galaxies actively feed on matter and gas, beaming out light as they do so. Our own Milky Way has a supermassive black hole at its centre, but it is currently inactive.
Mergers and interactions
But we still don't really understand how supermassive black holes form and evolve. Previous studies have shown that galaxy mergers could be part of the equation. Now, new high-quality data gathered by the Euclid satellite provide the strongest evidence yet, reported in a special edition of Astronomy and Astrophysics .
Using AI, scientists including UBC researcher Dr. Allison Man analyzed hundreds of thousands of mergers from up to 10 billion years ago. They found that AGN are two to six times more common in merging galaxies than in their non-merging counterparts.
The best and brightest
Mergers were most strongly associated with AGN cloaked in dust—cosmic heavyweights linked to rapid black hole growth as the AGN gobbles up the surrounding matter. These AGN are the brightest, outshining surrounding galaxies. Other, less bright supermassive black holes at the centre of galaxies were likely created through other means, the authors concluded.
"We're starting to explore just how supermassive black holes form and evolve, and to pin down the connection between galaxy mergers, supermassive black hole mergers and how they contribute to building up the most massive black holes in the universe," said Dr. Man.
