Galaxies trapped in web of a giant black hole

Astronomers have detected six galaxies lying around a supermassive black hole when the Universe was less than a billion years old.

It is the first time such a close grouping has been seen so soon after the Big Bang, they say, and the finding supports the theory that black holes can grow rapidly within large, web-like structures which contain plenty of gas to fuel them.

“These are extreme systems and to date we have had no good explanation for their existence,” says Marco Mignoli from Italy’s National Institute for Astrophysics (INAF), the lead author of a paper in Astronomy & Astrophysics.

The new observations – made with the ESO’s Very Large Telescope (VLT) – revealed that several galaxies surrounding the black hole were all lying in a cosmic “spider’s web” of gas extending to more than 300 times the size of the Milky Way.

“The galaxies stand and grow where the filaments cross, and streams of gas – available to fuel both the galaxies and the central supermassive black hole – can flow along the filaments,” Mignoli says.

The light from this very large structure, with its black hole of one billion solar masses, has travelled to us from a time when the Universe was only 900 million years old.  

The researchers believe the “spider’s web” and the galaxies within it contain enough gas to provide the fuel that the black hole needed to so quickly become a supermassive giant.

“Our finding lends support to the idea that the most distant and massive black holes form and grow within massive dark matter halos in large-scale structures, and that the absence of earlier detections of such structures was likely due to observational limitations,” says co-author Colin Norman, from Johns Hopkins University, US.

The galaxies are some of the faintest that current telescopes can see, and the discovery required observations over several hours with the largest optical telescopes available.

Using the MUSE and FORS2 instruments on the VLT at ESO’s Paranal Observatory in Chile, the team confirmed the link between four of the six galaxies and the black hole.

“We believe we have just seen the tip of the iceberg, and that the few galaxies discovered so far around this supermassive black hole are only the brightest ones,” says INAF co-author Barbara Balmaverde.

They, like other astronomers, are no doubt eagerly awaiting the arrival of ESO’s Extremely Large Telescope (ELT), currently being built Paranal Observatory and scheduled to be operational in 2025.

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