Time Machine Simulations

Astrophysicists create ‘Time Machine’ simulations to observe the life cycle of cities with ancestral galaxies

Scientists create ‘time machine’ simulations that study the life cycle of ancestral galaxy cities.

Many processes in astrophysics take a very long time, making their evolution difficult to study. For example, a star like our sun has a lifespan of about 10 billion years, and galaxies evolve over billions of years.

One way astrophysicists deal with this is by looking at different objects to compare them at different stages of evolution. They can also look at distant objects to effectively look back in time, because of the long time it takes for light to reach our telescopes. For example, if we look at an object 10 billion light-years away, we see it as it was 10 billion years ago.

Now, for the first time, researchers have created simulations that directly mimic the full life cycles of some of the largest collections of galaxies observed in the distant Universe 11 billion years ago, reports a new study published June 2, 2022 in the journal. Natural Astronomy

Cosmological simulations are crucial to studying how the universe came to be the shape it is today, but many do not match what astronomers observe through telescopes. Most are designed to match the real universe only in a statistical sense. On the other hand, limited cosmological simulations are designed to directly reproduce the structures we actually observe in the universe. However, most existing simulations of this kind have been applied to our local universe, ie close to Earth, but never to observations of the distant universe.

A team of researchers, led by Kavli Institute for the Physics and Mathematics of the Universe Project Researcher and first author Metin Ata and Project Assistant Professor Khee-Gan Lee, were interested in distant structures such as massive galaxy protoclusters, which are ancestors of today’s galaxy clusters before they could clump together under their own gravity. They found that current studies of distant protoclusters were sometimes too simple, meaning they were done with simple models and not simulations.

Screenshots of Time Machine Simulation

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

“We wanted to try to develop a full simulation of the real distant universe to see how structures started and how they ended,” Ata said.

Their result was COSTCO (COnstrained Simulations of The COsmos Field).

Lee said developing the simulation was a lot like building a time machine. Because light from the distant Universe is only now reaching Earth, the galaxies that telescopes observe today are a snapshot of the past.

“It’s like finding an old black and white photo of your grandfather and making a video of his life,” he said.

In that sense, the researchers took snapshots of “young” grandparent galaxies in the universe and then fast-forward their ages to study how galaxy clusters would form.

The light from galaxies the researchers used traveled a distance of 11 billion light-years to reach us.

The most challenging was taking into account the large-scale environment.

“This is something that is very important for the fate of those structures, whether they are isolated or associated with a larger structure. If you don’t consider the environment, you get very different answers. We have been able to consistently take into account the large scale environment, because we have a full simulation and therefore our prediction is more stable,” said Ata.

Another major reason the researchers created these simulations was to test the Standard Model of cosmology, which is used to describe the physics of the universe. By predicting the ultimate mass and ultimate distribution of structures in a given space, researchers could reveal previously undetected discrepancies in our current understanding of the universe.

Using their simulations, the researchers were able to find evidence of three already published galaxy protoclusters and reject one structure. In addition, they were able to identify five other structures that formed consistently in their simulations. This includes the Hyperion proto-supercluster, the largest and earliest proto-supercluster known today, which is 5000 times the mass of our[{” attribute=””>Milky Way galaxy, which the researchers found out it will collapse into a large 300 million light year filament.

Their work is already being applied to other projects including those to study the cosmological environment of galaxies, and absorption lines of distant quasars to name a few.

Details of their study were published in Nature Astronomy on June 2.

Reference: “Predicted future fate of COSMOS galaxy protoclusters over 11 Gyr with constrained simulations” by Metin Ata, Khee-Gan Lee, Claudio Dalla Vecchia, Francisco-Shu Kitaura, Olga Cucciati, Brian C. Lemaux, Daichi Kashino and Thomas Müller, 2 June 2022, Nature Astronomy.
DOI: 10.1038/s41550-022-01693-0

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