Collapse of dark matter may be the missing ingredient in explaining how supermassive black holes formed before the first stars.
A growing mystery in astronomy is the existence of massive black holes (some as heavy as a billion suns) that existed less than a billion years after the Big Bang. According to the standard theory of black hole formation, these black holes should not have had enough time to grow so large.
A new study led by Yash Agarwal, a graduate student at the University of California, Riverside, shows that the decay of dark matter may be the key to understanding the origins of these giant universes.
Published in Journal of Cosmology and Astroparticle Physicsthis study shows that the energy released from the collapse of dark matter could change the chemistry of early galaxies enough that some galaxies could collapse directly into black holes rather than forming stars.
The results are timely as NASA’s James Webb Space Telescope continues to observe unusually large black holes in the early universe that may have formed by direct collapse. Astronomers believed the process required the coincidence of a nearby star glowing on the prostar gas, so they expected it to be rare.
Agarwal’s team goes beyond the standard approach by using dark matter, the 85% of the unknown matter in the universe that helps form galaxies. They showed that when dark matter decays, a small amount of its energy leaks into the gas, which can directly accelerate the rate of decay. Each decaying dark matter particle only needs to inject an amount of energy that is one billionth of the energy of a single AA battery.
“Our research suggests that the collapse of dark matter could profoundly alter the evolution of the first stars and galaxies, with far-reaching consequences for the entire Universe,” Agarwal said.
“As the James Webb Space Telescope reveals more supermassive black holes in the early Universe, this mechanism may help bridge the gap between theory and observation.”
Flip Taned, an associate professor of physics and astronomy at UCR and Agarwal’s doctoral assistant, said ideas related to this research had been floating around in his group since 2018.
“The first galaxies were essentially primordial balls of hydrogen gas, and their chemistry is incredibly sensitive to atomic-scale energy injections,” says Tanedo, a co-author of the paper.
“These are the properties we look for in dark matter detectors. These ‘detector’ characteristics could be the supermassive black holes we see today.”
A research team including James Dent of Sam Houston State University in Texas and Tao Xu of the University of Oklahoma modeled the thermochemical dynamics of gas in the presence of collapsing axions and found that a dark matter mass window of 24 to 27 electron volts could create conditions that directly seed collapsing black holes.
Tanedo points out that this research was the result of a series of fortuitous events that brought together the right people at the right time, including a series of workshops that brought together particle physicists, cosmologists and astrophysicists to discuss big questions in the field.
“We showed that the right dark matter environment helps make the ‘coincidence’ of a direct collapse of a black hole much more likely,” he says.
“Similarly, support for interdisciplinary research helped enable the ‘serendipity’ that led to this study.”
This research was supported by the National Science Foundation and a UCR Hellman Fellowship.
Source: University of California, Riverside
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