In A First, Time Machine Simulations Created To Understand Lifecycle Of Largest Galaxy Clusters

For the first time, scientists have created 'time machine' simulations which directly recreate the full cycle of some of the largest collections of galaxies observed in the distant universe.

Colourful galaxy

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For the first time, scientists have created 'time machine' simulations which directly recreate the full cycle of some of the largest collections of galaxies observed in the distant universe. These galaxy clusters are 11 billion light-years away from us. The findings of the study, led by scientists at University of Tokyo, were recently published in the journal Nature Astronomy.

In order to determine how the universe became the shape it is today, it is very important to have cosmological simulations. However, many simulations do not typically match what astronomers observe through telescopes. Most simulations are designed to match the real universe only in a statistical sense. 

How Do Constrained Cosmological Simulations Help Astronomers?

On the other hand, constrained cosmological simulations are designed to directly reproduce the structures we actually observe. According to a statement released by the University of Tokyo, most existing simulations of this kind have been applied to our local universe, but never for observations of the distant universe.

The study team was interested in distant structures like massive galaxy protoclusters, which are ancestors of present-day galaxy clusters before they could clump under their own gravity. The researchers found current studies of distant protoclusters were sometimes oversimplified, which means they were done with simple methods and not simulations. 

According to the statement, Metin Ata, the first author of the study, said the scientists wanted to try developing a full simulation of the real distant universe to see how structures started out and how they ended. Their result was COSTCO (COnstrained Simulations of The COsmos Field), the study said.

Khee-Gan Lee, one of the authors on the paper, said developing the simulation was much like building a time machine. The galaxies that telescopes observe today are a snapshot of the past because light from the distant universe is only reaching Earth now.

Lee said it is like finding an old black-and-white picture of your grandfather and creating a video of his life.

Astronomers Took Snapshots Of 'Young' Grandparent Galaxies

According to the statement, the scientists took snapshots of "young" grandparent galaxies in the universe and then fast-forwarded their age to study how clusters of galaxies would form. The light from the galaxies observed as part of the study travelled a distance of 11 billion light-years to reach Earth, the study said.

Taking the large scale environment into account was a challenging task.

Ata said this is something that is very important for the fate of those structures whether they are isolated or associated with a bigger structure. He added that the environment is not taken into account, then completely different answers will be obtained. 

The researchers were able to take the large scale environment into account consistently, because they have a full simulation, Ata said. He added that this is why their prediction is more stable.

Also, the researchers created these simulations to test the standard model of cosmology, which is used to describe the physics of the universe. Scientists could unveil previously undetected discrepancies in our current understanding of the universe by predicting the final mass and final distribution of structures in a given space, the statement said.

The scientists were able to find evidence of three published galaxy protoclusters, and disfavour one structure, by using these simulations. The study team was also able to identify five more structures which consistently formed in their simulations, including the Hyperion proto-supercluster. This is the largest and earliest proto-supercluster known today which is 5,000 times the mass of our Milky Way galaxy. 

According to the statement, the findings are being applied to other projects including those to study the cosmological environment of galaxies, and absorption lines of distant quasars, the brightest objects in the universe.