DCU-led team finds answer to puzzling origin of supermassive black holes

13 Mar 2017

The massive black hole (left) in this drawing is able to rapidly grow as intense radiation from a galaxy nearby shuts down star formation in its host galaxy. Image: John Wise/Georgia Tech

An international team led by DCU researcher John Regan has solved one the universe’s biggest puzzles: what led to the formation of supermassive black holes?

It was more than a decade ago that supermassive black holes were discovered but, since then, their origin has remained a complete mystery.

Believed to have grown and grown over billions of years, the dozen astronomical behemoths that have been discovered so far are thought to have originated just 800m years after the Big Bang, which occurred 13.8bn years ago.

Seemingly defies astrophysics

However, Dublin City University (DCU) postdoc researcher Dr John Regan and his team of international researchers may have found substantial evidence to back one particular formation theory.

The theory suggests that these giants rapidly accumulated mass during the early formation of the universe, as molecular hydrogen cooled and deflated a primordial plasma of hydrogen and helium to form stars and galaxies.

While this environment should make it difficult for supermassive black holes to form, a 2008 study suggested that radiation from a massive neighbouring galaxy could cause a nascent black hole and its host galaxy to collapse, rather than spawn new clusters of stars.

Now, according to the latest research published in Nature Astronomy, computer simulations have shown that a black hole can rapidly grow at the centre of its host galaxy if a nearby galaxy emits enough radiation to switch off its capacity to form stars.

With this typical astrophysical trait disabled, the host galaxy grows until its eventual collapse, creating an enormous monster that swallows everything from dying stars to other black holes.

Much faster growth than expected

Previous estimates suggested that a neighbouring galaxy would have to be at least 100m times more massive than our sun to emit enough radiation to prevent star formation.

However, the supercomputer recruited to simulate the birth of a supermassive black hole showed that the nearby galaxy could be smaller and closer than previously estimated, and can only occur within a ‘Goldilocks zone’ of distance.

“The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years – a blip in cosmic time,” said study co-author Zoltan Haiman.

“A few hundred million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected.”

The findings were made by a team of researchers from DCU, Columbia University, Georgia Tech and the University of Helsinki.

Colm Gorey was a senior journalist with Silicon Republic