The James Webb Space Telescope (JWST) has uncovered an extraordinary event in the early universe: a merger involving at least five galaxies, occurring approximately 800 million years after the Big Bang. This unprecedented discovery challenges existing models of galaxy formation and suggests that complex interactions among galaxies began much earlier than previously believed.
Researchers, led by Dr. Weida Hu, a postdoctoral researcher, and Dr. Casey Papovich, a professor of physics and astronomy, published their findings in the journal Nature Astronomy. The newly identified system, referred to as “JWST’s Quintet,” reveals multiple galaxies interacting within a surprisingly compact area, surrounded by a halo of oxygen-rich gas.
At this early stage in cosmic history, astronomers anticipated that galaxies would generally remain small and isolated. Contrary to this expectation, the Quintet demonstrates that significant mergers could occur in the universe’s infancy. “What makes this remarkable is that a merger involving such a large number of galaxies was not expected so early in the universe’s history,” Hu explained.
Unprecedented Star Formation Rates
The system was identified through data from the JWST Advanced Deep Extragalactic Survey, one of the most extensive imaging campaigns conducted with the telescope. Although the galaxies are separated by tens of thousands of light-years, they are situated within a compact region and are forming stars at a rate approximately 250 times the mass of the Sun per year. This rate far exceeds that of typical galaxies during this period.
The researchers discovered an extended halo of glowing gas that connects several of the galaxies. This gas emits light from ionized oxygen and hydrogen, and intriguingly, it exists outside the galaxies themselves. The presence of these heavy elements, primarily produced in stars, indicates that they are being expelled from the galaxies during the collision. The analysis suggests that gravitational interactions during the merger, rather than galactic winds, are primarily responsible for this enrichment.
Implications for Galaxy Evolution Models
Dr. Papovich emphasized the significance of this discovery, stating, “By showing that a complex, merger-driven system exists so early, it tells us our theories of how galaxies assemble — and how quickly they do so — need to be updated to match reality.” This finding may help clarify why the JWST has detected an increasing number of massive galaxies that appear largely inactive just a few billion years later. If systems like JWST’s Quintet merged rapidly and exhausted their gas early, they could evolve into the massive galaxies observed at later times.
Future JWST observations aim to further explore the motion of gas and galaxies within this system, which could provide deeper insights into how early cosmic structures formed.
The research also included contributions from Texas A&M University, with co-authors Dr. Lu Shen, a postdoctoral research associate; Dr. Justin Spilker, an assistant professor; and Justin Cole, a Ph.D. student. Funding for this research was provided by the Kavli Institute for Theoretical Physics, NASA, and Marsha and Ralph Schilling.
Overall, the findings from the James Webb Space Telescope not only reveal fascinating aspects of the early universe but also prompt a reevaluation of theoretical frameworks regarding galaxy formation and evolution.
