Nearly every large galaxy hosts a supermassive black hole at its centre, but sometimes these enormous objects may bounce away from the middle of their home. A new search has found nine such off-centre black holes, which may help us figure out how supermassive black holes formed.
In the early universe, galaxies and black holes formed and evolved together. Supermassive black holes are the most massive objects in any galaxy, so they inevitably ended up in the centres of their galaxies.
But over time, galaxies crash together and merge. When their separate black holes have different masses or spin in different directions, the recoil can send the final, combined object flying off towards the galaxy鈥檚 edge at up to 500 kilometres per second, where it can remain for millions or billions of years before drifting back towards the centre.
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at the University of Maryland and her colleagues sifted through data on 5493 active galactic nuclei 鈥� supermassive black holes that release huge amounts of light 鈥� from the Zwicky Transient Facility in California. They found nine that appear to be products of mergers and were pushed away from the centres of their galaxies.
If confirmed, these could help disentangle the effects of the formation of black hole seeds from the effects of mergers, helping us solve the mystery of how supermassive black holes form.
鈥淏ecause these events are very dramatic and extreme, every time a candidate is presented in the literature, it鈥檚 met with a lot of very justified scepticism because it鈥檚 very hard to prove that it was a recoil event,鈥� says Ward. The team plans to examine the candidates in more detail and continue to look for more strange, off-centre black holes.
The Astrophysical Journal
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