The new study was published in the January 2023 issue of The Astrophysical Journal.
The unexpectedly lonely galaxy 3C 297, discovered 9.2 billion light-years from Earth, has challenged existing theories on galaxy formation. Researchers suggest it may be the most distant "fossil group" ever discovered, where one galaxy has absorbed its former companions.
This result made with NASA’s Chandra X-ray Observatory and the International Gemini Observatory may push the limits of how quickly astronomers expect galaxies to grow in the early universe.
The unexpectedly large galaxy is located about 9.2 billion light-years from Earth and contains a quasar, a supermassive black hole pulling in gas at the centre of the galaxy and driving powerful jets of matter seen in radio waves. The environment of this galaxy, known as 3C 297, appears to have the key features of a galaxy cluster: enormous structures that usually contain hundreds or even thousands of galaxies. Yet 3C 297 stands alone.
and her colleagues see two key traits of a galaxy cluster in the Chandra X-ray data. First, the X-ray data reveals the lone galaxy is surrounded by large quantities of gas with temperatures of tens of millions of degrees — something normally seen in galaxy clusters.
Despite having these important features of a galaxy cluster, Missaglia’s team’s data from the Gemini Observatory in Hawaii revealed that none of the 19 galaxies that appear close to 3C 297 in a Gemini optical image, and that have accurate distance measurements, are actually at the same distance as the lonely galaxy.
While many other fossil groups have been detected before, this one is particularly distant, at 9.2 billion light-years away. (The previous record holders for fossil groups were at distances of 4.9 and 7.9 billion light-years.)
The authors cannot rule out the presence of dwarf galaxies around 3C 297, but their presence would still not explain the lack of larger galaxies like the Milky Way. Nearby examples include M87 in the Virgo Cluster, which has had large galactic companions for billions of years. However, 3C 297 will spend billions of years essentially alone.