04 October 2022
Cold flows created the first quasars
Published online 14 July 2022
Quasars that appeared surprisingly quickly in the early universe probably formed due to cold flows in rare gas clouds.
A cosmological modelling study could help explain how some quasars formed soon after the Big Bang. The work, by a team, including Muhammad Latif at United Arab Emirates University in Al-Ain, UAE, and Daniel Whalen at Portsmouth University, UK, suggests that cold, turbulent streams in some rare gas reservoirs were able to create supermassive stars, which collapsed to form black holes.
Latif and Whalen have previously investigated how, when, and where gigantic black holes can form, and how big they can get. They turned their attention to the puzzling observation, 20 years ago, of quasars that formed less than a billion years after the Big Bang. Theorists have struggled to explain how these bright objects – which have black holes at their centres — could have appeared so quickly.
“The problem with the conventional scenarios for massive black hole formation is that they require rather exotic conditions, such as an intense UV flux from a nearby active star-forming galaxy,” explains Latif. “Scientists believed that without strong UV radiation, a gas cloud would fragment and form multiple stars. With UV, this fragmentation is suppressed, so the entire cloud can collapse into a massive black hole.”
To investigate an alternative route, the researchers used Enzo, an open-source multi-physics simulation code that is ideal for studying how cosmological structures form and evolve. They ran their models on the high-performing cluster at UAE University, with initial conditions informed by the PLANCK mission, which measured cosmic microwave background radiation to a very high precision. This leftover energy from the Big Bang gives clues about density fluctuations in the infant universe that later turned into the galaxies and other structures we see today.
The novel black-hole-forming mechanism revealed by Latif and co-workers does not require the presence of UV, and is a natural consequence of cold dark matter cosmology.
“Our simulations showed that large, cold flows of gas can generate strong turbulence, which does not allow normal stars to form,” says Latif. “Instead, two supermassive stars of more than 30,000 solar masses formed, which directly collapsed into black holes within just a few million years.”
Latif and Whalen are confident that their work opens a whole new line of research, and are already planning more detailed investigations.
“We hope that the upcoming observations from the James Webb Space Telescope will help us to constrain our model and ultimately reveal the origin of the first supermassive black holes,” says Latif.
Astrostatistician, Daniel Mortlock of Imperial College London, UK, comments, "The simulations look very promising as a physically-motivated explanation for the super-massive black holes we see powering the most distant quasars. A number of previous theories had hypothesised the existence of similarly massive black hole 'seeds' at early times, but were not able to provide such a complete physical picture of how such objects formed. That said, there is still much work to be done to bolster this result. It’s difficult to verify such complicated numerical codes when applied to unusual settings. And while such black hole seeds are apparently necessary to explain the quasars we see, it hasn’t yet been shown that those seen in these simulations have formed in the sort of larger environment necessary for them to grow by a further factor of a million in mass over the following few hundred million years."
Latif, M.A. et al. Turbulent cold flows gave birth to the first quasars. Nature https://doi.org/10.1038/s41586-022-04813-y (2022).