Photo: Joshua Worth via Creative Commons
Observations by the James Webb Space Telescope have shown that galaxies became surprisingly massive within the first billion years after the Big Bang. Yet only another billion years later, many of them stopped forming new stars and effectively began to die.
Until now, scientists believed powerful stellar winds could shut down galaxies, but lacked direct evidence. An international team of astronomers has now described how these winds suppress star formation, creating the population of dormant galaxies observed by James Webb, according to Live Science.
For the study, researchers combined observations from the James Webb Space Telescope and the ALMA observatory to examine a galaxy system known as CRISTAL-02, which formed just one billion years after the Big Bang.
With a stellar mass about 10 billion times that of the Sun, CRISTAL-02 is the product of multiple galaxy mergers in their final stages. The system also features a massive gas plume stretching nearly the length of the galaxy itself and moving through space at hundreds of kilometers per second.
The outflow contains roughly 1.5 billion solar masses of gas. Researchers say it was generated by intense stellar winds triggered by a burst of star formation and the deaths of massive stars. During galaxy mergers, giant clouds of gas collapse to create new stars, including extremely massive ones that explode as supernovae just a few million years later.
The powerful winds produced by these young and dying stars inject enormous amounts of energy into the surrounding gas, dispersing the cold molecular clouds needed to create future generations of stars.
"The galaxy is driving an extremely powerful stellar wind, ejecting material at roughly twice the rate it is forming stars," said lead author Rebecca Davis, an astrophysicist at Swinburne University of Technology in Australia.
Although CRISTAL-02 is estimated to produce around 260 Sun-like stars every year—about three times more than galaxies of similar mass—it is losing more than 500 solar masses of gas annually, around 20 times faster than typical massive galaxies.
"We know very little about how the first galaxies stopped forming stars. This work provides direct evidence of that process in action. If the gas outflow continues, the galaxy will exhaust the fuel needed for star formation in less than 100 million years—a blink of an eye on cosmic timescales," said co-author Andreas Faisst, an observational astronomer at the California Institute of Technology.
Earlier, James Webb also discovered a stellar bridge in the galaxy GN20 that formed just 1.5 billion years after the Big Bang.
