A new study shows that galaxies in the young Universe were disorderly and struggled to settle in, like cosmic babies.
Using powerful James Webb Space Telescope (JWST), scientists have studied more than 250 galaxies in the early Universe. The research team mapped the movement of gas long ago when the Universe was growing – between 800 million and 1.5 billion years after the Big Bang. (Space is approximately 13.8 billion years.)
“Most of the galaxy's population is experiencing a turbulent phase in its evolutionary history,” the lead author said. Rolliadoctoral student at the Kavli Institute of Cosmology at the University of Cambridge, told Live Science in an email.
Unlike previous studies, Dunhive explained, the team targeted less massive galaxies and found what they called “promiscuous kinematics,” meaning the galaxies the researchers studied are not stable, spinning disks such as Milky Way and his neighbors.
Turbulence in the early history of the universe was much higher than scientists previously thought, Dunhive added, because earlier studies were biased toward larger, more orderly galaxies that are easier to detect with telescopes than the smaller galaxies examined in the new study.
“We find evidence that this turbulence in [galaxy] The disk is caused by a large amount of gas, which fuels intense star formation and causes gravitational instability,” Dunhive said.
Moreover, the researchers mapped how galaxies evolved from these chaotic structures into the more regular structures observed in mature galaxies, providing unprecedented insight into how galaxies evolved from youth to maturity.
“Early on, galaxies experience a turbulent assembly phase, when strong bursts of star formation and large amounts of gas disrupt the orderly motion of the gas disk,” Dunhive said. “At later times, galaxies increase their mass and become more stable.”
Structures like Milky Way formed very recently, in the last few billion years, as available gas was consumed by stars and diminished in the galaxy as a whole. Less free-floating gas allows mature galaxies to grow and change more smoothly than when they were younger.
The research would not have been possible without JWST, which is located in a remote, gravitationally stable location in space, far from the scattered light of the Earth and Moon. The infrared telescope can peer deeper into space than any of its predecessors and regularly discovers galaxies believed to be earliest in the known universe. Dunhive said the observatory, combined with modeling, is helping researchers better understand “explosive” star formation and how gas affects the galaxy's disk.
“Overall, our work provides a window into the formation dynamics of early galaxies,” she said. Next, the team plans to study the inflows and outflows of gas in individual galaxies, tracking how the gas was chemically enriched.
Researchers expect the incoming gas to be less enriched, or “intact“, while the escaping gas will contain more chemical components due to the contribution of individual stars within the galaxy. Studying how gas flows throughout a galaxy can allow researchers to understand, for example, why some galaxies spin faster than others.
“There is so much more to discover with JWST's amazing capabilities, and we look forward to exploring many more aspects of early galaxy formation,” Dunhive said.
