Rare quasar triplet forms one of the most massive objects in the universe

Ultramassive black holes are the most massive objects in the universe. Their mass can reach millions and billions of solar masses. Supercomputer simulations on the Texas Advanced Computing Center’s (TACC) Frontera supercomputer have helped astrophysicists reveal the origins of ultramassive black holes formed about 11 billion years ago.

“We found that a possible formation channel for ultramassive black holes is from the extreme merger of massive galaxies that is most likely to occur in the epoch of the ‘cosmic dinner,'” said Yueying Ni, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics.

Ni is the main author of work published in The Astrophysical Journal Letters in December 2022 that found ultramassive black holes from the merger of triple quasars, systems with three galactic cores lit by gas and dust collapsing into a nested supermassive black hole.

Working hand in hand with telescope data, computational simulations help astrophysicists fill in the missing pieces about the origins of stars and exotic objects such as black holes.

One of the largest cosmological simulations to date is called Astrid, developed by Ni. It is the largest simulation in terms of the particle, or memory load in galaxy formation simulations.

“The science goal of Astrid is to study galaxy formation, the merging of supermassive black holes and re-ionization over cosmic history,” she explained. Astrid models large volumes of the cosmos that span hundreds of millions of light years, but can zoom in to very high resolution.

Ni developed Astrid using the Texas Advanced Computing Center’s (TACC) Frontera supercomputer, the most powerful academic supercomputer in the US

“Frontera is the only system we did (in) Astrid from day one. It’s a pure Frontera-based simulation,” Ni continued.

Frontera is ideal for Nis Astrid simulations because of its ability to support large applications that need thousands of compute nodes, the individual physical processor systems, and the memory built together for some of science’s toughest calculations.

“We used 2,048 nodes, the maximum allowed in the large queue, to start this simulation on a routine basis. It is only possible on large supercomputers like Frontera,” Ni said.

Her findings from the Astrid simulations show something completely unimaginable – the formation of black holes can reach a theoretical upper limit of 10 billion solar masses. “It is a very computationally challenging task. But you can only capture these rare and extreme objects with a large-volume simulation,” Ni said.

“What we found are three ultramassive black holes that accumulated their mass during the cosmic dinner, the time 11 billion years ago when star formation, active galactic nuclei (AGN) and supermassive black holes in general reach their peak activity,” she added.

About half of all the stars in the universe were born during cosmic noon. Evidence for that comes from multi-wavelength data from a number of galaxy surveys such as the Great Observatory’s Origins Deep Survey, where the spectra of distant galaxies tell the stars’ ages, star formation histories and the chemical elements of the stars within.

“In this epoch, we saw an extreme and relatively rapid merger of three massive galaxies,” Ni said. “Each of the galaxy masses is 10 times the mass of our own Milky Way, and a supermassive black hole sits at the center of each galaxy. Our findings raise the possibility that these quasar triplet systems are the progenitors of the rare ultramassive black holes, after these triplets gravitationally interact and merge together.”

Moreover, new observations of galaxies at cosmic noon will help to reveal the coalescence of supermassive black holes and the formation of the ultramassive ones. Data is rolling in now from the James Webb Space Telescope (JWST), with high-resolution details of galaxy morphologies.

“We are pursuing a mock-up of observations for JWST data from the Astrid simulation,” Ni said.

“In addition, the future space-based NASA Laser Interferometer Space Antenna (LISA) Gravitational Wave Observatory will give us a much better understanding of how these massive black holes merge and/or coalesce, along with the hierarchical structure, formation and galaxy mergers along cosmic history, ” she added. “This is an exciting time for astrophysicists, and it’s good that we can have simulation to allow theoretical predictions for these observations.”

Ni’s research group is also planning a systematic study of AGN hosts for galaxies in general. “They are a very important science target for JWST, determining the morphology of the AGN host galaxies and how they differ compared to the broad population of galaxies during cosmic noon,” she added.

“It’s great to have access to supercomputers, technology that allows us to model a patch of the universe in great detail and make predictions from the observations,” Ni said.