Astronomers have captured a strange phenomenon that has never been observed before: very distant dwarf galaxies about to merge, accompanied by a giant black hole at their center. What’s more, not just one, but two pairs have been spotted!
Two new candidates for “doubly active galactic nuclei” have just been found by a team of researchers, explains a study accepted in The Astrophysical Journal and prepublished on ArXiv. The phenomenon has been theorized for a long time, but very little has been observed until now. More specifically, it is a merger of supermassive black holes located at the centers of galaxies. And not just any: dwarf galaxies with fewer than a billion stars. In comparison, the Milky Way contains 200 to 400 billion!
And this type of merger is of particular interest because the very first galaxies, far from reaching the size of the Milky Way, were dwarf galaxies. They then merged into the galaxies we know today. “Most of the dwarf galaxies and black holes in the early Universe are likely to have grown much larger by now through repeated mergers,” study co-author Brenna Wells said in a statement. In a way, dwarf galaxies are our galactic ancestors that evolved over billions of years into large galaxies like our own Milky Way.
Captured from black hole accretion disks
Imaged by NASA’s Chandra X-ray Observatory, the two pairs of galaxies named Mirabilis and Elstir & Vinteuil are 760 million light-years and 3.2 billion light-years away, respectively. They were discovered on the accretion disk of their central black holes: the matter falling towards the black hole heats up to millions of degrees and forms a plasma disk around the star, which emits a large amount of X-rays!
The first pair, Mirabilis, are in the late stages of fusion and display a long tail caused by the tidal effects of the collision. Conversely, Elstir & Vinteuil is just beginning, gradually forming a bridge of stars and gas connecting the two galaxies. “Follow-up observations of these two systems will allow us to study processes critical to understanding galaxies and their young black holes,” concluded study co-author Jimmy Irwin.