Scientists have discovered that a sample of galaxies from the first two to three billion years of the universe appear to be much hotter and contain much heavier elements than they should.
We can see farther back in time the deeper we look into space. It takes billions of years for light from some of the younger galaxies in our universe to reach us and be detected by our instruments. This light is full of cosmic dawn information. Furthermore, this light has the ability to reveal not only our past but also our potential future.
A team of astrophysicists led by Northwestern University has examined data from the James Webb Space Telescope (JWST), which peered back to realms that formed just two-to-three billions of years after the Big Bang, in order to comprehend the evolution of several of these early universe, "teenage" galaxies.
Some fascinating surprises have emerged from the observations.
The group specifically examined data from the Chemical Evolution Constrained using Ionised Lines in Interstellar Aurorae (CECILIA) Survey and discovered that these galaxies appear to host heavy elements such as nickel in addition to appearing hotter than expected.
In the Hubble Space Telescope image at the top, light from 23 distant galaxies—represented by red rectangles—was combined to capture extremely faint emission from eight different elements, labelled in the JWST spectrum at the bottom. Astronomers hardly ever, if ever, see many of these elements in distant galaxies, despite the fact that scientists routinely discover them on Earth. (Photo courtesy of Northwestern, CIERA + IT-RCDS; Aaron M. Geller)
The scientists dedicated a full thirty hours to studying 33 far-off galaxies. Then, using a combination of light wavelengths from 23 of those galaxies, they were able to create a composite image of the structure's activity. These spectra provide information about potential components and average temperatures of the galaxies.
"This helps us understand an average galaxy better, but it washes out the details of individual galaxies. In a statement, Allison Strom, Northwestern University assistant professor of physics and astronomy and the study's lead author, added, "It also enables us to see fainter features."
Eight distinguishable elements were present in the composite image of the galaxies: silicon, sulphur, argon, nitrogen, oxygen, hydrogen, and nickel. The presence of nickel, which is heavier than iron in the periodic table, was somewhat unexpected, even though the lighter elements were predicted.
"Never in my wildest dreams did I imagine we would see nickel," Strom stated.
Nickel is rarely observed, even in older, nearby galaxies. This is because nickel is formed after multiple star life cycles, which means multiple rounds of supernovae and the chance for heavier elements to synthesise and spread throughout the galaxy.
"Never does anyone discuss seeing nickel. For us to see elements in gas, they must be glowing. Therefore, there might be something special about the stars within the galaxies that allows us to see nickel," Strom said.
"Ultimately, the fact that we see a higher characteristic temperature is just another manifestation of their different chemical DNA because the temperature and chemistry of gas in galaxies are intrinsically linked," says Strom, suggesting that the higher observed temperatures in these early galaxies may be related in some way to their unusual chemical composition.
The Astrophysical Journal Letters published the study on November 20.