Photo: Joshua Worth з Creative Commons CC-BY license
Astronomers have for the first time identified a possible reason why some massive galaxies in the early Universe suddenly stopped forming new stars. Powerful galactic winds appear to be blowing away the cold gas needed for star formation, according to a study published in the Monthly Notices of the Royal Astronomical Society.
The mystery of the "dead" galaxies
During the first 1–2 billion years after the Big Bang, galaxies were rapidly growing and merging to form larger cosmic structures. However, observations by the James Webb Space Telescope (JWST) have revealed surprisingly massive galaxies that already appeared "dead" or inactive at an early stage of cosmic history.
These galaxies had previously experienced intense bursts of star formation but later produced very few new stars. Scientists had proposed several explanations, but a new study led by Rebecca Davies of Swinburne University of Technology points to a process in which galaxies effectively exhaust their own supply of star-forming material.
A destructive wind in CRISTAL-02
Researchers examined CRISTAL-02 as it appeared roughly 1 billion years after the Big Bang. The object appears to be the result of a major collision involving at least two galaxies.
Such mergers can drive large amounts of gas toward the center of a galaxy, triggering an intense burst of star formation. However, this process can also set off a destructive chain reaction.
CRISTAL-02 was forming stars at roughly twice the rate of comparable galaxies from the same era. Massive stars then quickly reached the end of their lives and exploded as supernovae.
The combined effect of these explosions generated a powerful galactic wind that pushed cold gas out of the system. This gas is the primary raw material required to form new stars.
According to the researchers, gas is currently escaping from CRISTAL-02 at roughly twice the rate at which new stars are forming. If this continues, the galaxy could exhaust its available gas in less than 50 million years and eventually become inactive.
A common process in the early Universe
Nearly half of the massive galaxies in the early Universe were actively interacting with neighboring galaxies. This suggests that powerful galactic winds may have been a widespread mechanism that caused some galaxies to stop forming stars, rather than an isolated phenomenon.
The findings could also help astronomers improve computer models of galaxy evolution. Scientists plan to conduct further observations with the JWST to study dusty regions of CRISTAL-02 and search for other early galaxies whose development may have been halted by powerful stellar and galactic winds.
