In dwarf galaxies, two pairs of supermassive black holes are on a collision track. The black holes were discovered using NASA’s Chandra X-ray Observatory and represent the first evidence of an approaching collision. The occurrence could supply scientists with crucial knowledge regarding the genesis of black holes in the early Universe as well as the history of dwarf galaxies. These galaxies have stars with a total mass of fewer than 3 billion Suns, or roughly 20 times that of the Milky Way.
Scientists have long theorized that dwarf galaxies combine, particularly in the early Universe, to form the bigger galaxies we observe today. The initial generation of dwarf galaxy mergers, however, cannot be observed with current equipment. Collisions between the pairs of dwarf galaxies revealed in a recent study have dragged gas into the gigantic black holes they each possess, forcing the black holes to develop. Since they are extremely dim at such great distances, the earliest dwarf galaxies are impossible to view with modern equipment.
“Astronomers have discovered numerous examples of black holes on collision trajectories in nearby big galaxies. But, searches for them in dwarf galaxies are significantly more difficult and have previously failed,” said Marko Micic of the University of Alabama, who led the study.
Deep Chandra X-ray observations were compared to infrared data from NASA’s Wide Infrared Survey Explorer (WISE) and optical data from the Canada-France-Hawaii Telescope (CFHT). The researchers looked for pairs of strong X-ray sources in colliding dwarf galaxies as evidence of two black holes and found two. Although one pair was discovered in Abell 133, a galaxy cluster 760 million light-years from Earth, the other pair was identified in Abell 1758S, a galaxy cluster 3.2 billion light-years away.
“We’ve discovered the first two distinct pairings of black holes in merging dwarf galaxies. We can drill down into issues concerning the first galaxies, their black holes, and star formation triggered by collisions by using these systems as analogs for ones in the early universe,” o-author Olivia Holmes noted.
The merging dwarf galaxies in Abell 1758S were dubbed “Elstir” and “Vinteuil” by the astronomers after imaginary artists from Marcel Proust’s “In Search of Lost Time.” The features of merging black holes and dwarf galaxies may reveal information about our Milky Way’s past. Astronomers believe that nearly all galaxies began as dwarf or other types of tiny galaxies and developed through mergers over billions of years.