Astronomers simulate life cycle of oldest galaxies in universe

It’s impossible to relive the past but astronomers can simulate certain aspects of it. Now, researchers have simulated the life cycle of the biggest and oldest galaxies in the visible universe.

The researchers behind the study set out to simulate the evolution of a large cluster of budding galaxies, called massive galaxy protoclusters. These structures began populating the universe about 3 billion years after the big bang and eventually formed into present-day galaxy clusters.

Astronomers have created several simulations that mirror parts of the universe close to Earth, but not far away. This moved the scientists to develop a simulation of more distant regions of the universe.

“We wanted to try developing a full simulation of the real distant universe to see how structures started out and how they ended,” says Metin Ata, a cosmologist at the University of Tokyo who led the study, in a statement. He adds that developing the simulation felt like creating a time machine.

Screenshots from the simulation show (top) the distribution of matter corresponding to the observed galaxy distribution at a light travel time of 11 billion years (when the Universe was only 2.76 billion years old or 20% its current age), and (bottom) the distribution of matter in the same region after 11 billion lights years or corresponding to our present time. (Credit: Ata et al.)

The protoclusters span 11 billion light-years away, making them among the most ancient and distant structures astronomers can observe. Ata and his colleagues captured snapshots of the protoclusters to help simulate their life cycles, which they could rewind and fast forward like a movie.

“It’s like finding an old black-and-white picture of your grandfather and creating a video of his life,” Ata says.

The biggest hurdle the team encountered while performing the study was including the entire scale of these massive structures in the simulation, which can affect experimental outcomes. “If you don’t take the environment into account, then you get completely different answers,” Ata explains. “We were able to take the large-scale environment into account consistently, because we have a full simulation, and that’s why our prediction is more stable.”

Cosmological simulations allow scientists to test different models about how the universe works. The standard model of cosmology is the prevailing model in physics that describes the relationship between elementary particles and three of the four forces of nature. Consequently, the researchers put the standard model to the test using the simulation.

The simulation provided evidence for three out of four galaxy protoclusters. Five other structures also repeatedly formed in the team’s simulation, including the Hyperion protosupercluster, the largest and oldest cluster of forming galaxies ever found.

“We also discover previously unknown protoclusters with lower final masses than are typically detectable by other methods that nearly double the number of known protoclusters within this volume,” the researchers wrote.

The study reportedly marks the first simulation of the entire life cycle of protoclusters.

The study is published in the journal Nature Astronomy.


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