Simulation of Black Hole Ejection
This simulation shows a collision between a pair of spiral galaxies leading to a merger between their supermassive black holes and an ejection of the new black hole that forms. This represents a model for the formation and evolution of the exotic X-ray source CID-42.
The galaxy collision causes long tails of stars to be thrown out of each galaxy. After the collision the two black holes (labelled by circles) initially located at the center of each galaxy orbit around each other until they eventually merge. The newly formed black hole recoils from the directional emission of gravitational waves produced by the collision, giving the newly merged black hole a sufficiently large kick for it to eventually escape from the galaxy. The simulation freezes briefly to make a comparison with the HST optical image, at a time about 6 million years after the merger. The speed of the black hole at this time is over three million miles per hour, compared to the escape velocity of the galaxy of only about 1.7 million miles per hour.
The masses of the two galaxies are about 450 billion and 230 billion times the mass of the sun, with stars forming throughout the simulation. The masses of the two black holes just before they merge are about 5.4 and 4.3 million times the mass of the sun, giving a total of about 10 million solar masses for the new black hole. Both black holes grow considerably during the galaxy collision.
The total duration of the movie is 2 billion years, with the merger and ejection of the black hole occurring after 1.9 billion years. The movie runs at half speed after the merger so the eye can track the black hole flying out of the galaxy. The recoiling black hole could be detectable, by radiation from material in a surrounding disk, for several million years after the time of the observation. By the end of the simulation, the BH has virtually exhausted its gas supply and is moving, invisible, through intergalactic space.
(Credit: Laura Blecha)