Galaxies typically create stars from their vast clouds of dust and gas. However, an intriguing discovery by the James Webb Space Telescope (JWST) unveils a galaxy that has remained starless for a staggering 13 billion years.
This galaxy, dubbed JADES-GS-z7-01-QU, and its peculiar behavior were detailed in a study posted last year on arXiv and subsequently published in Nature on March 6.
Star Formation
The galaxy derives its name from the JWST Advanced Deep Galactic Survey (JADES), the initiative responsible for its observation.
Upon analysis, the research team concluded that the galaxy likely experienced a brief burst of star formation lasting between 30 million to 90 million years. However, it appears to have ceased producing stars merely 10 million to 20 million years before the timeframe in which we observe it. Considering that its light has traveled over 13 billion years to reach us, JWST perceives it as it existed just 700 million years post the Big Bang, marking it as the oldest "dead" galaxy discovered to date.
A galaxy can halt its star-forming activities when its central supermassive black hole absorbs the interstellar reservoir of dust necessary for star creation. Alternatively, a galaxy may deplete its dusty resources by forming stars too rapidly, inadvertently starving itself and halting all new star formation. The team remains uncertain about the specific cause observed with JWST. However, studying ancient galaxies aids astronomers in unraveling the mysteries of galactic evolution and star formation, thereby refining existing models.
The phenomenon of galaxies abruptly ceasing star formation is not new to astronomers. By the time the universe reached 3 billion years in age, approximately half of its massive galaxies had halted star formation. Observations from the Hubble Space Telescope and ESO's Very Large Telescope suggest that in dormant galaxies, star formation ceases at their core and gradually fizzles out from within. These galaxies, like the elliptical galaxy IC 2006, only produce stars on the outer edges of their disks.
So, why do galaxies undergo this star factory shutdown? It could be due to factors preventing gas from replenishing within galaxies, as indicated by a 2021 study in Nature. Additionally, galaxy collisions and mergers may play a significant role. Research published in the Astrophysical Journal Letters suggests that in merging galaxies, gas may be heated or stripped to the point where it can no longer foster star nurseries post an initial burst. (Hot gas lacks the propensity to form stars as readily as cold gas.)
The JADES team aims to shed further light on this enigma. Francesco D'Eugenio, a study co-author and researcher at the Kavli Institute for Cosmology, expressed, "We're searching for other galaxies resembling this one in the early universe, which will aid us in understanding how and why galaxies cease star formation. It's possible that galaxies in the early universe 'die' only to rejuvenate later — additional observations will be instrumental in deciphering this puzzle."
Space Telescope