For the past year and a half, the James Webb Space Telescope has provided stunning images of distant galaxies formed shortly after the Big Bang, giving scientists their first glimpse of the fledgling universe. Now, a group of astrophysicists has taken the next step: Find the smallest, brightest galaxies near the beginning of time, or scientists will have to completely revise their theories about dark matter.

A composite of Stephan’s Quintet, a visual group of five galaxies, created from nearly 1,000 separate image files from the James Webb Space Telescope. UCLA astrophysicists believe that if cold dark matter theories are correct, the Webb Telescope should find small, bright galaxies in the early universe. Image credit: NASA

The team, led by UCLA astrophysicists, ran simulations that tracked the formation of small galaxies after the Big Bang and for the first time ignored interactions between gas and dark matter. They found that the galaxies created are much smaller, much brighter, and form faster than typical simulations that do not take these interactions into account, instead showing much fainter galaxies.

Small galaxies, also known as dwarf galaxies, exist throughout the universe, and are often thought to be The oldest type of galaxy. Thus, small galaxies are particularly interesting to scientists studying the origins of the universe. But the small galaxies they find don’t always match what they think they should be looking for. Those closest to the Milky Way rotate as quickly or are not as dense as the simulations, indicating that the models may have left something out, such as these gas-dark matter interactions.

New research published in Astrophysical Journal Letters, It improves the simulation by including the interactions of dark matter with the gas and shows that these faint galaxies may have been much brighter than expected early in the universe’s history, when they were just beginning to form. The authors suggest that scientists should try to find smaller galaxies that are brighter than expected using telescopes like the Webb Telescope. If they are only faint, some of their ideas about dark matter may be wrong.

Dark matter is a type of hypothetical matter that does not interact with electromagnetism or light. Thus, it is impossible to observe using optics, electricity or magnetism. But dark matter interacts with gravity, and its presence is inferred from the effects of gravity on ordinary matter – the stuff that makes up the entire observable universe. Although 84% of the matter in the universe is thought to be made up of dark matter, this has never been the case. Found out Straight

All galaxies are surrounded by a vast halo of dark matter, and scientists believe that dark matter was necessary for their formation. “Standard Cosmological ModelAstrophysicists use the term galaxy formation to describe how clumps of dark matter in the very early universe gravitationally entered ordinary matter, forming stars and the galaxies that We are watching today. Because most dark matter particles—called cool dark matter—are thought to move much slower than the speed of light, the accretion process must have been gradual.

But 13 billion years ago, before the first galaxies formed, ordinary matter and dark matter, composed of hydrogen and helium gas from the Big Bang, were moving relative to each other. The gas passes through dense clumps of dark matter moving slower than supersonic speeds that it should have pulled in to form galaxies.

“In fact, in models that don’t take streaming into account, that’s exactly what happens,” said Claire Williams, a UCLA doctoral student and first author of the paper. “Gas is attracted by the gravity of dark matter, forming clumps and knots that can cause hydrogen fusion, and thus form stars like our Sun.”

But Williams and co-authors on The supersonic project The team, a group of astrophysicists from the United States, Italy and Japan, is led by a UCLA professor of physics and astronomy. summer nose, They found that if they included in the simulations the streaming effect of the different velocities between dark matter and normal matter, the gas fell far away from the dark matter and was immediately stopped from forming stars. When the accreted gas fell back into the galaxy millions of years later, a massive burst of star formation occurred simultaneously. Because these galaxies for a time had many more young, hot, bright stars than normal small galaxies, they shone much brighter.

“While streaming suppressed star formation in small galaxies, it also promoted star formation in dwarf galaxies, causing them to overtake the non-streaming patches of the Universe,” Williams said. “We predict that the Webb Telescope will be able to find regions of the Universe where galaxies are bright, rising at this speed. The fact that they’re so bright makes it difficult for the telescope to see these small galaxies.” It could make it easier to discover galaxies, which are usually very difficult to detect just 375 million years after the Big Bang.

Because dark matter is impossible to study directly, searching for bright fragments of galaxies in the early universe could provide an effective test for theories about dark matter, which have so far been inconclusive.

“The discovery of patches of small, bright galaxies in the early universe would confirm that we are on the right track with the cool dark matter model because only the acceleration between two types of matter can produce these types of galaxies. That’s what we’re looking for,” said Knouse, the Howard and Astrid Preston Professor of Astrophysics. “If dark matter does not behave like standard cool dark matter and the streaming effect is not present, these bright dwarf galaxies will not be found and we need to go back to the drawing board.”

The research was supported by the National Science Foundation and NASA.

written by Holy Uber

Source: UCLA