Young galaxy CRISTAL-02 faces rapid star formation shutdown due to powerful gas expulsion

Astronomers have made a significant discovery regarding a young galaxy system, CRISTAL-02, that appears to be expelling the gas essential for star formation. This finding sheds light on an intriguing phenomenon observed in the early Universe by the James Webb Space Telescope, specifically the abundance of so-called “dead” galaxies from that time period.

CRISTAL-02, observed just 1.1 billion years post-Big Bang, does not represent a tranquil galaxy but rather a chaotic collection of star-forming regions in the throes of a final cosmic collision. This violent interaction has funneled gas into denser areas, sparking a furious rate of star production. However, it seems that this same collision might also be leading to the galaxy’s eventual shutdown.

Using the capabilities of both the James Webb Space Telescope and the Atacama Large Millimeter/submillimeter Array, researchers have identified a massive plume of cold gas extending approximately 7,000 light-years from CRISTAL-02. This gas is being expelled in a powerful wind, not due to an active black hole, but as a result of energy released from supernova explosions of short-lived massive stars.

Dr. Rebecca Davies, the lead author of the study from Swinburne University of Technology in Australia, described the dense regions of the universe as akin to bustling urban environments where galaxies collide and erupt in star formation. However, the aftermath of massive stars igniting in supernovae generates winds that can blow away the gas required for future star formation.

This phenomenon can lead to what researchers term a “galaxy-killing wind.” When galaxies cease forming new stars, they are categorized as dead or quiescent. Although their existing star population might endure for billions of years, the lack of a cold gas reservoir halts their growth.

Interestingly, the James Webb Space Telescope has detected a surprisingly high number of massive dead galaxies in the early Universe, a period when galaxies were just one to two billion years old. This observation posed challenges to existing models of galaxy evolution, as such rapid growth followed by an abrupt end was unexpected. Some explanations had suggested more complex early-Universe physics, including unusual behaviors of dark energy.

In contrast, the recent findings propose a more simpler scenario: violent galaxy mergers could instigate intense bursts of star formation that subsequently unleash winds capable of depleting a galaxy’s gas supply.

CRISTAL-02 is currently forming stars at an impressive rate of about 260 solar masses annually, which is approximately three times higher than anticipated for a galaxy of its size at this stage in cosmic history. However, the gas outflow is occurring at a staggering rate of about 520 solar masses per year, effectively doubling the star formation rate. If this trend persists without the infusion of new gas, the galaxy could exhaust its supply of molecular gas in just a few tens of millions of years.

Davies warned, “The galaxy has a powerful wind that is ejecting material twice as fast as the galaxy forms stars. If this rapid blowout continues, the galaxy could be dead in less than 50 million years.”

The research team used data from ALMA to detect cold gas and the Near Infrared Spectrograph on JWST to observe warmer ionized gas, together revealing a wind that exhibits various physical states. The projected outflow, moving at about 640 kilometers per second, indicates that some gas might escape the gravitational grasp of CRISTAL-02 entirely.

Importantly, the researchers found no current evidence of an active supermassive black hole fueling the wind; however, they acknowledged that earlier black-hole activity could have contributed to the phenomenon.

If CRISTAL-02 serves as a typical example, this mechanism could be prevalent among early massive galaxies, as the study indicates that nearly half of these systems are involved in major mergers. Such cosmic collisions not only drive gas inward and spark intense star formation but can also unleash winds that curtail or entirely halt this process.

Davies concluded, “Almost half of early massive galaxies are interacting with other nearby galaxies, suggesting this isn’t a quirk but a widespread cosmic phenomenon. CRISTAL-02 offers a natural solution to the mystery of why these massive galaxies live fast and die young.”