Astronomers have discovered a 'galaxy-killing wind' that may explain why there are far more massive 'dead' galaxies than expected in the early universe.

This wind, powered by cosmic collisions of galaxies, could quickly blow away all the fuel for new stars, leaving the galaxy on the brink of death and helping to solve one of the biggest mysteries in modern astrophysics.

The theory is much simpler than some of the other explanations put forward since 2022, when the James Webb Space Telescope (JWST) gave us our first clear glimpse of the early universe. Among them was that dark energy may have been stronger in the early universe than current theories predict, allowing galaxies to grow and die faster.

Researchers behind the new study, published today in Monthly Notices of the Royal Astronomical Society: Letters, used JWST to show that galaxy-killing winds can be powered by the same intense star-formation that causes galaxies to grow rapidly, explaining why these early galaxies live fast and die young.

"Dense regions of the universe are like very active cities," said lead author Dr Rebecca Davies, of the Swinburne University of Technology in Melbourne, who carried out the study with Associate Professor Deanne Fisher.

"Galaxies collide and undergo frenzied bursts of star-formation. But when the biggest stars burn out, they explode as supernovae, launching powerful winds that blast away the very gas galaxies need to keep forming stars."

Galaxy winds have long been considered prime suspects for the deaths of massive galaxies, but observational evidence was lacking.

Using JWST and the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope, the Swinburne team imaged a galaxy one billion years after the Big Bang in the midst of a rapid growth spurt.

This galaxy, called CRISTAL-02, is forming stars twice as fast as other similar-sized galaxies. The extremely sensitive observations revealed a huge plume of cold gas extending far away from CRISTAL-02. This plume is almost as long as the galaxy itself, which is a telltale sign that gas is being driven out of the galaxy.

"The galaxy has a powerful wind that is ejecting material twice as fast as the galaxy forms stars," Dr Davies added.

"If this rapid blowout continues, the galaxy could be dead in less than 50 million years: explaining the origin of the mysterious massive dead galaxies in the early universe."

CRISTAL-02 is not a single galaxy, but multiple galaxies in the final stages of a cosmic collision. During such collisions, gas funnels towards the galaxy centres, triggering strong bursts of star formation.

Dr Davies believes that other galaxies will likely face a similar fate to CRISTAL-02, undergoing frenzied bursts of star-formation, followed by powerful winds that lead them to their deaths.

"Almost half of early massive galaxies are interacting with other nearby galaxies, suggesting this isn’t a quirk but a widespread cosmic phenomenon," she said.

"If many early galaxies collide and experience rapid growth, then it may not be surprising that we see so many dead galaxies in the early universe.

"CRISTAL-02 offers a natural solution to the mystery of why these massive galaxies live fast and die young."

ENDS

Media contacts

Sam Tonkin

Royal Astronomical Society

Mob: +44 (0)7802 877 700

press@ras.ac.uk

Science contacts

Dr Rebecca Davies

Swinburne University of Technology

rdavies@swin.edu.au

Images & captions

CRISTAL-02

Caption: An artist’s impression of the galaxy CRISTAL-02, with a huge plume of cold gas extending away from it. This plume is almost as long as the galaxy itself, which is a telltale sign that gas is being driven out of the galaxy.

Credit: Joshua Worth via Creative Commons CC-BY license

Further information

The paper 'Multiphase images of a powerful supernova-driven wind in the early Universe’ by Davies et al. has been published in Monthly Notices of the Royal Astronomical Society: Letters. DOI: 10.1093/mnras/stag874

Notes for editors

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