Physicists have solved a mystery related to JWST-ER1g, an ancient galaxy that formed when the universe was only a quarter of its current age. Last September, the James Webb Space Telescope (JWST) discovered this massive galaxy, which is associated with an Einstein ring. This is because JWST-ER1g acts as a lens and bends light from a distant source, causing it to appear as a ring. This phenomenon, known as strong gravitational lensing, was predicted in Einstein’s theory of general relativity.The mass inside the Einstein radius consists of two parts: stellar and dark matter components. Hai-Bo Yu, a professor at the University of California, Riverside, explained that by subtracting the stellar mass from the total mass, the dark matter mass within the Einstein radius can be obtained. However, the calculated dark matter mass was higher than anticipated, which raised questions. In their paper published in The Astrophysical Journal Letters, the team presented an explanation for this puzzling discrepancy. The dark matter halo is an invisible halo surrounding a galaxy.Dark matter is a crucial component that surrounds and permeates galaxies like JWST-ER1g. Even though it has not been observed in laboratories, physicists are certain that dark matter, constituting 85% of the universe’s matter, is real.
“When regular matter, such as pristine gas and stars, collapses and condenses into the dark matter halo of JWST-ER1g, it may cause the halo to compress, leading to a higher density,” explained Demao Kong, a second-year graduate student at UCR who led the analysis. “Our numerical studies demonstrate that this process can account for the high density of dark matter in JWST-ER1g, resulting in a greater mass of dark matter within the same volume, and consequently a higher density.”
According to a paper co-authored by Daneng Yang, a postdoctoral researcher at UCR, the formation of JWST-ER1g 3.4 billion years after the Big Bang presents a valuable opportunity to study dark matter.
Yang explained that this particular strong lensing object is special because it features a perfect Einstein ring, which can provide important information about the total mass within the Einstein radius. This is a crucial step in testing the properties of dark matter.
Launched on Christmas Day in 2021, NASA’s JWST, also known as Webb, is an orbiting infrared observatory with the purpose of addressing fundamental questions about the universe.It is the most extensive, intricate, and potent space telescope ever constructed.
“JWST offers an unprecedented chance to observe ancient galaxies that formed during the early stages of the universe,” Yu stated. “We anticipate discovering more unexpected findings from JWST and gaining a better understanding of dark matter in the near future.”
The research was funded by the John Templeton Foundation and the U.S. Department of Energy.
The research paper, “Cold Dark Matter and Self-interacting Dark Matter Interpretations of the Strong Gravitational Lensing Object JWST-ER1,” is available for open access.