A galaxy that suddenly stopped forming recent stars greater than 13 billion years ago has been observed by astronomers.
Using the James Webb Space Telescope, a world team of astronomers led by the University of Cambridge have spotted a ‘dead’ galaxy when the universe was just 700 million years old, the oldest such galaxy ever observed.
This galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for therefore early within the universe’s evolution. Nonetheless, it’s unclear whether this galaxy’s ‘quenched’ state is temporary or everlasting, and what caused it to stop forming recent stars.
The outcomes, reported within the journal Nature, may very well be essential to assist astronomers understand how and why galaxies stop forming recent stars, and whether the aspects affecting star formation have modified over billions of years.
“The primary few hundred million years of the universe was a really lively phase, with numerous gas clouds collapsing to form recent stars,” said Tobias Looser from the Kavli Institute for Cosmology, the paper’s first writer. “Galaxies need a wealthy supply of gas to form recent stars, and the early universe was like an all-you-can-eat buffet.”
“It’s only later within the universe that we begin to see galaxies stop forming stars, whether that is because of a black hole or something else,” said co-author Dr Francesco D’Eugenio, also from the Kavli Institute for Cosmology.
Astronomers consider that star formation will be slowed or stopped by various factors, all of which can starve a galaxy of the gas it must form recent stars. Internal aspects, resembling a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas will be consumed in a short time by star formation, without being promptly replenished by fresh gas from the environment of the galaxy, leading to galaxy starvation.
“We’re undecided if any of those scenarios can explain what we have now seen with Webb,” said co-author Professor Roberto Maiolino. “Until now, to grasp the early universe, we have used models based on the fashionable universe. But now that we will see a lot further back in time, and observe that the star formation was quenched so rapidly on this galaxy, models based on the fashionable universe may should be revisited.”
Using data from JADES (JWST Advanced Deep Extragalactic Survey), the astronomers determined that this galaxy experienced a brief and intense period of star formation over a period between 30 and 90 million years. But between 10 and 20 million years before the time limit where it was observed with Webb, star formation suddenly stopped.
“The whole lot seems to occur faster and more dramatically within the early universe, and which may include galaxies moving from a star-forming phase to dormant or quenched,” said Looser.
Astronomers have previously observed dead galaxies within the early universe, but this galaxy is the oldest yet — just 700 million years after the massive bang, greater than 13 billion years ago. This statement is one in every of the deepest yet made with Webb.
Along with the oldest, this galaxy can be relatively low mass — in regards to the same because the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, although the SMC remains to be forming recent stars. Other quenched galaxies within the early universe have been way more massive, but Webb’s improved sensitivity allows smaller and fainter galaxies to be observed and analysed.
The astronomers say that even though it appears dead on the time of statement, it’s possible that within the roughly 13 billion years since, this galaxy could have come back to life and began forming recent stars again.
“We’re in search of other galaxies like this one within the early universe, which can help us place some constraints on how and why galaxies stop forming recent stars,” said D’Eugenio. “It may very well be the case that galaxies within the early universe ‘die’ after which burst back to life — we’ll need more observations to assist us figure that out.”
The research was supported partially by the European Research Council, the Royal Society, and the Science and Technology Facilities Council (STFC), a part of UK Research and Innovation (UKRI).
