DCU researchers central to solving cosmic riddle on the birth of massive black holes in the early universe

Researchers from Dublin City University’s Centre for Astrophysics and Relativity (CfAR) have been centrally involved in a major breakthrough with the discovery of a new pathway that explains the existence of massive black holes in the universe and predicts a greater number than previously thought.

The light released from around the first massive black holes in the Universe is so intense it is able to reach our telescopes across the entire expanse of the Universe. The light from the most distant black holes (or quasars) has been travelling towards earth for more than 13 billion light-years, allowing us to look back in time to the early universe. However, how these monster black holes formed remained unknown; until now.

Dr John Regan and Prof. Turlough Downes, DCU in collaboration with a research team from Georgia Institute of Technology, Michigan State University, the University of California at San Diego, the San Diego Supercomputer Center and IBM have discovered a new and extremely promising avenue for solving this cosmic riddle.

The team showed that when galaxies assemble extremely rapidly, and sometimes violently, it can lead to the formation of a massive black hole. The rapid assembly of gas means that instead of normal star formation proceeding, embryonic stars become puffed up by hot gas. This leads to the formation of what is called a “supermassive” star. Supermassive stars can only survive for a short time before quickly collapsing into a massive black hole.

The new study turns upside down the long-accepted belief that massive black hole formation could only happen in regions bombarded by powerful radiation from nearby galaxies. This research shifts that paradigm and opens up a whole new area of research.

Conclusions of the study are reported in the journal Nature and supported by funding from the US National Science Foundation, the European Union and NASA.

“At first when we found these black hole formation sites in the simulation we were stumped. Previous theories suggested this should only happen when the sites were exposed to high levels of star-formation killing radiation. As we delved deeper we saw that these sites were undergoing a period of extremely rapid growth. That was the key! The violent and turbulent nature of the rapid assembly, the violent crashing together of the galaxy’s foundations during the galaxy’s birth prevented normal star formation and led to perfect conditions for black hole formation instead,” said Dr John Regan, Research Fellow  in the Centre for Astrophysics and Relativity in Dublin City University and author on the study.

“Our next goal is to probe the further evolution of these exotic objects. Where are these black holes today? Can we detect evidence of them in the local Universe or with gravitational waves?” commented Dr Regan.

“Astronomers observe supermassive black holes that have grown to a billion solar masses in 800 million years,” said Dr John Wise from Georgia Institute of Technology and corresponding author of the study. A solar mass is the mass of our own Sun. “Doing that required an intense convergence of mass in that region. You would expect that in regions where galaxies were forming at very early times.”

“One of the biggest scientific challenges in this kind of work is being able to figure out what happens in a large portion of the Universe, while still being able to detect what’s going on in important, but small regions – remember that in comparison to the size of the Universe even a super-massive black hole is really tiny. The Renaissance Simulations of the early Universe, on which this research is based, achieve this by working out “on the fly” where interesting things are happening and focusing a lot of effort there.

However, even with this extremely efficient method, this work is so challenging that there is no way to get these unique insights into our Universe without the use of some of the world’s largest supercomputers,” commented Professor Turlough Downes, Director of the Centre for Astrophysics and Relativity at Dublin City University and author on the study.