What is it about galaxies and dark matter? Most, if not all, galaxies are surrounded by a halo of this mysterious, unknown, but ubiquitous matter. It also played a role in the formation of galaxies. Astronomers are still figuring out the nature of its role. Now they are exploring the nascent universe, searching for the smallest and brightest galaxies. That’s because it could help tell the story of dark matter’s role in the creation of galaxies.
An international team of astronomers led by UCLA’s Smadar Naoz is simulating the early formation of galaxies. Their computer program tracks the birth of galaxies shortly after the Big Bang. These “new” computer models include a few new wrinkles. They take into account the hitherto ignored interaction between dark matter and the primordial “matter” of the universe. They are hydrogen and helium gas. The simulation results: Small, bright galaxies formed faster than computer models that did not include these motions. Astronomers just need to use JWST to find them to see if the dark matter theory holds.
Interaction between dark matter and supersonic baryonic matter
How does the interaction between baryonic matter and dark matter make a difference? Here’s one likely story. In the early universe, clouds of gas moved past clumps of dark matter at supersonic speeds. It was bounced off by dark matter. Eventually, after millions of years, the gaseous material fell back down and formed stars in a star-birthing explosion. The researchers’ simulations tracked the formation of these galaxies shortly after the Big Bang.
Naoz’s team believes that the presence of these smaller, brighter and more distant galaxies could support the so-called “cold dark matter” model. This suggests that after the Big Bang, the universe was in a hot, dense state containing only gas. Over time, it evolved into a clumpy distribution of galaxies (eventually galaxy clusters). Stars and galaxies were formed during this process, with the first stage likely relying on gravitational interactions with dark matter. If the supersonic interactions modeled by Naoz’s team actually occurred, they would result in the formation of small galaxies.
Simulation of galaxy formation and the influence of dark matter
JWST observed some very early galaxies during its operations. The oldest one has not yet been detected. But the images it provided are intriguing hints at what existed in earlier times, and could provide insight into the role of dark matter. It is therefore natural for astronomers to want to push their views back as far as possible. And that means looking for bright spots of light that existed hundreds of millions of years after the Big Bang.
“The discovery of small, bright patches of galaxies in the early universe would confirm that we are on the right orbit with the cold dark matter model, because the only velocity between two types of matter is the “can produce the kind of galaxies we’re looking for,” Naoz said. “If the dark matter does not behave like standard cold dark matter and streaming effects are not present, then these bright dwarf galaxies will not be found and we will have to go back to square one.”
A paper by team member and lead author Claire Williams ( Astrophysics Journal Letter) The research team suggests that scientists using JWST will start looking for galaxies that are much brighter than expected. If they exist, it would likely prove that the interaction occurred early in cosmic time. If nothing is found, perhaps scientists don’t yet understand how dark matter interacts. The big questions to answer are, if they exist, how did they form so quickly and why are they so bright?
Streaming through the Dark Matter Corridor
Let’s examine it by looking at the role of dark matter. The standard cosmological model maintains that the gravitational pull of a clump of dark matter in the early universe attracted ordinary matter. Eventually, it led to the formation of stars and subsequently galaxies. Dark matter is thought to move more slowly than light. Therefore, astronomers predicted that the process of forming stars and galaxies would occur very slowly. At least, that’s what previous simulations suggest.
But what if something different had happened more than 13 billion years ago? How would that change things? It was a time before the first galaxies were formed. But that was a time when ordinary matter in the form of large superdensities of hydrogen and helium gas was flowing through the expanding universe. It bounced off the slow-moving mass of dark matter, overcoming its gravity, at least temporarily. Then, under the influence of dark matter, the baryonic matter gathered together again. Then the star is born fireworks began.
“While streaming suppressed star formation in the smallest galaxies, it also promoted star formation in dwarf galaxies, making them brighter than non-streaming parts of the Universe,” Williams said. Essentially, the accumulated gas started falling together after millions of years. This led to the formation of massive stars. Many hot, young stars began to shine, outshining the stars of other small galaxies. What this ultimately means is that dark matter is impossible to “see”, so these bright specks of galaxies could be indirect evidence of the existence of dark matter. . And they will prove the role dark matter played in the formation of galaxies.
find bright patches
No one has yet figured out exactly what Naoz and the team are looking for. If realized, it would go a long way toward gaining insight into the role of cold dark matter. “The discovery of small, bright patches of galaxies in the early universe would confirm that we are on the right orbit with the cold dark matter model, because the only velocity between two types of matter is the “can produce the kind of galaxies we’re looking for,” Naoz said.
Of course, JWST is the perfect telescope to view these galaxies. It should be possible to peer into regions of the universe that contain small, young galaxies that are brighter than astronomers expect. This extreme brightness helped JWST discover them and shows them when the universe was only a few hundred million years old. Since it is impossible to study dark matter directly, searching for bright patches of baby galaxies in the early universe could effectively test theories about dark matter and its role in the formation of the first galaxies. There is a gender.
For more information
Bright galaxies test dark matter
Supersonic Project: Illuminating the faint edge of the JWST UV brightness function
