Dusty supermassive black holes are fuelled by galaxies on collision course

Supermassive black holes with masses millions or billions of times greater than that of our Sun reside at the centres of galaxies, including our Milky Way. They grow by feeding on the gas that falls on to them, but the mechanism behind bringing gas close enough to facilitate this process remains a mystery.

A new study, led by researchers from Newcastle University, has found that dusty supermassive black holes are more likely to grow and release tremendous amounts of energy when they are inside galaxies that are on a collision course with a neighbouring galaxy. The growing black holes were found using infrared light, which is produced by the hot dust surrounding them.

The team conducting this study used data from the NASA/ESA Hubble Space Telescope, the Spitzer Space Telescope and other observatories.

The researchers devised a new technique to assess the probability of two galaxies being in close proximity and on a collision course in the future. Using this new method, they analyzed a vast number of galaxies in the distant universe, galaxies that formed between 2 to 6 billion years after the Big Bang, to gain a deeper understanding of "cosmic noon," a period when most of the universe's galaxy and black hole growth is expected to have occurred.

"Our novel approach looks at hundreds of thousands of distant galaxies with a statistical approach and asks how likely any two galaxies are to be close together and so likely to be on a collision course," said Sean Dougherty, postgraduate student at Newcastle University and lead author of the paper.

The researchers hope to find many more of these hidden growing black holes using the James Webb Space Telescope (JWST). Webb's ability to look farther into space than ever before will help reveal even more secrets about how these dusty black holes grow.

"JWST will be far better at finding them, therefore we will have many more to study, including ones that are the most difficult to find. From there, we can do more to understand the dust that surrounds them, and find out how many are hidden in distant galaxies," said Dr Chris Harrison, a researcher at Newcastle University's School of Mathematics, Statistics and Physics and co-author of the study,