Virtual ‘Universe Machine’ Sheds Light On Galaxy Evolution

Eddie Gonzales Jr. – MessageToEagle.com – Using computer simulations, astronomers created millions of virtual universes and comparing them to observations of actual galaxies.

Thus, a UA-led research team has contributed with a powerful new approach for studying galaxy formation.

How do galaxies such as our Milky Way come into existence? How do they grow and change over time?

A UA-led team of scientists generated millions of different universes on a supercomputer, each of which obeyed different physical theories for how galaxies should form. (Image: NASA, ESA, and J. Lotz and the HFF Team/STScI

Now, researchers are one step closer to finding answers thanks to supercomputer simulations.

“On the computer, we can create many different universes and compare them to the actual one, and that lets us infer which rules lead to the one we see,” Peter Behroozi, an assistant professor at the UA Steward Observatory, the study’s lead author, said in a press release.

The study is the first to create self-consistent universes that are such exact replicas of the real one: computer simulations that each represent a sizeable chunk of the actual cosmos, containing 12 million galaxies and spanning the time from 400 million years after the Big Bang to the present day.

Each “Ex-Machina” universe was put through a series of tests to evaluate how similar galaxies appeared in the generated universe compared to the true universe. The universes most similar to our own all had similar underlying physical rules, demonstrating a powerful new approach for studying galaxy formation.

The results from the “UniverseMachine,” have helped resolve the long-standing paradox of why galaxies cease to form new stars even when they retain plenty of hydrogen gas, the raw material from which stars are forged.

Commonly held ideas about how galaxies form stars involve a complex interplay between cold gas collapsing under the effect of gravity into dense pockets giving rise to stars, while other processes counteract star formation.

“As we go back earlier and earlier in the universe, we would expect the dark matter to be denser, and therefore the gas to be getting hotter and hotter.  This is bad for star formation, so we had thought that many galaxies in the early universe should have stopped forming stars a long time ago,” Behroozi said. “But we found the opposite: galaxies of a given size were more likely to form stars at a higher rate, contrary to the expectation.”

In order to match observations of actual galaxies, the researchers had to create virtual universes in which the opposite was the case – universes in which galaxies kept churning out stars for much longer.

If, on the other hand, the researchers created universes based on current theories of galaxy formation – universes in which the galaxies stopped forming stars early on – those galaxies appeared much redder than the galaxies we see in the sky.

Paper

Written by Eddie Gonzales Jr. – MessageToEagle.com Staff