Q Continuum computer simulation models birth of universe

This series shows the evolution of the universe as simulated by a run called the Q Continuum, performed on the Titan supercomputer and led by Argonne physicist Katrin Heitmann. These images give an impression of the detail in the matter distribution in the simulation. At first the matter is very uniform, but over time gravity acts on the dark matter, which begins to clump more and more, and in the clumps, galaxies form. Image credit: Heitmann et. al.

Researchers are sifting through an avalanche of data produced by one of the largest cosmological simulations ever performed, led by scientists at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory.

The simulation, run on the Titan supercomputer at DOE’s Oak Ridge National Laboratory, modelled the evolution of the universe from just 50 million years after the Big Bang to the present day — from its earliest infancy to its current adulthood. Over the course of 13.8 billion years, the matter in the universe clumped together to form galaxies, stars, and planets; but we’re not sure precisely how.

This series illustrates the universe's evolution as simulated by the Q Continuum run on the Titan supercomputer, overseen by Argonne physicist Katrin Heitmann. These visuals depict the intricate matter distribution within the simulation. Initially, the matter exhibits uniformity, but as time progresses, gravity influences the dark matter, causing it to aggregate, leading to the formation of galaxies within these clusters. Image credit: Heitmann et. al. Researchers are analyzing vast amounts of data generated by one of the most extensive cosmological simulations ever conducted, led by experts at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory. Executed on the Titan supercomputer at DOE’s Oak Ridge National Laboratory, the simulation portrays the universe's development from a mere 50 million years post-Big Bang to the present day — from its nascent stages to its current state. Throughout 13.8 billion years, cosmic matter coalesced to give rise to galaxies, stars, and planets; however, the exact mechanisms remain uncertain. These simulations aid scientists in comprehending dark energy, a force influencing the universe's expansion rate, encompassing the distribution of galaxies comprising ordinary matter and enigmatic dark matter, which has eluded direct observation thus far. Extensive sky surveys conducted using advanced telescopes such as the Sloan Digital Sky Survey and the more detailed Dark Energy Survey pinpoint the locations of galaxies and stars at the time of their initial light emission. Additionally, investigations into the Cosmic Microwave Background, residual light from the universe's infancy at 300,000 years old, unveil the universe's initial state — described by Katrin Heitmann, the leading physicist at Argonne, as "initially uniform, with matter clustering over time." The simulation bridges the temporal gap, illustrating the universe's potential evolution: "Gravity influences dark matter, prompting increased aggregation and the eventual formation of galaxies," as stated by Heitmann.

Galaxies have halos surrounding them, which may be composed of both dark and regular matter. This image shows a substructure within a halo in the Q Continuum simulation, with “subhaloes” marked in different colours. Image credit: Heitmann et al.

The Q Continuum simulation involved half a trillion particles, dividing the universe into cubes with sides 100,000 kilometers long. This marks one of the largest cosmology simulations at such high resolution, utilizing over 90 percent of the supercomputer. Typically, less than one percent of jobs on the Mira supercomputer at Argonne use 90 percent of its capacity, as noted by officials at the Argonne Leadership Computing Facility. Staff from Argonne and Oak Ridge computing facilities collaborated to adapt the code for running on Titan. "This simulation is very comprehensive," stated Heitmann. "We can analyze why galaxies cluster in this manner, along with the fundamental physics of structure formation." Analysis has commenced on the two and a half petabytes of generated data, a process expected to continue for several years. Researchers can extract data on various astrophysical phenomena like strong lensing, weak lensing shear, cluster lensing, and galaxy-galaxy lensing. The simulation code, Hardware/Hybrid Accelerated Cosmology Code (HACC), was initially developed in 2008, coinciding with the era when scientific supercomputers surpassed the petaflop barrier. HACC's design flexibility allows it to operate on supercomputers with diverse architectures. The study detailing this work, titled "The Q Continuum Simulation: Harnessing the Power of GPU Accelerated Supercomputers," was published in August in the Astrophysical Journal Supplement Series by the American Astronomical Society. Additional scientists from Argonne involved in the study were Nicholas Frontiere, Salman Habib, Adrian Pope, Hal Finkel, Silvio Rizzi, Joe Insley, and Suman Bhattacharya, alongside Chris Sewell from DOE's Los Alamos National Laboratory.