A new mathematical model shows how two merging supermassive black holes could produce a recoiling black hole ejected from its galaxy at high speed. The work offers a possible origin for a candidate runaway black hole identified in 2023 observations.
Researchers led by Tousif Islam at the University of California, Santa Barbara developed the model using simulations and observations. It indicates that the runaway black hole would result from the merger of two parent black holes, with one spinning rapidly and six times more massive than the other. The merger would have occurred about 70 million years ago, producing a recoil kick large enough to eject the resulting black hole.
The team found such strong recoils occur in fewer than 10 percent of black hole mergers. Digvijay Wadekar of the University of Texas at Austin described the approach as working backwards from the observed object, similar to fossil analysis.
Not all astronomers accept the runaway black hole interpretation. Jorge Sánchez Almeida at the Institute of Astrophysics of the Canary Islands and colleagues argue the observed line-like feature is an edge-on galaxy viewed from Earth. Future observations with the James Webb Space Telescope could distinguish between the two explanations.