Astronomers have spotted, for the first time, a trio of supermassive galaxies already fully formed in the first billion years of the universe’s existence.
These scarlet star makers – identified through imaging and spectrograph data by the James Webb Space Telescope (JWST) – challenge long-held notions that supermassive galaxies formed only after much longer periods of time, according to the researchers.
“It is a bit like looking at rocks from the earliest times in Earth’s history and seeing fossils of fully formed animals,” said Pieter van Dokkum, Sol Goldman Family Professor of Astronomy and Professor of Physics in Yale’s Faculty of Arts and Sciences, who is co-author of a new study, published in Nature, describing the discovery.
The international team of researchers, led by scientists at the University of Geneva, identified the trio of early galaxies using data from JWST’s FRESCO (First Reionization Epoch Spectroscopic Complete) survey. FRESCO is able to accurately measure distances and masses of galaxies.
The Webb telescope's unparalleled capabilities have allowed astronomers to systematically study galaxies in the very distant and early universe, providing insights into massive and dust-obscured galaxies. By analysing galaxies in the FRESCO survey, scientists found that most fit existing models. However, they also found three surprisingly massive galaxies that have roughly the same number of stars as today’s Milky Way.
These galaxies are also forming new stars at a rate that is nearly twice as high as their lower-mass counterparts and galaxies formed at later times, the researchers found. Due to their high dust content, which gives them a distinct red appearance in JWST images, they have been named the three “Red Monsters”.
Mengyuan Xiao, lead author of the study and a postdoctoral researcher at the University of Geneva, said: “Our findings are reshaping our understanding of galaxy formation in the early universe.”
The prevailing model of galaxy formation suggests that galaxies are mostly composed of dark matter and gas initially. This gas, a combination of hydrogen and helium, is slowly turned into stars as a galaxy ages. At most, it was thought, only about 20% of this gas is converted into stars in galaxies.
But Van Dokkum and his colleagues found that supermassive galaxies in the early universe may have been much more efficient at converting gas into stars.
“Somehow, these galaxies managed to turn nearly all of their gas into stars in just a few hundred million years – the blink of a cosmological eye,” Van Dokkum said.
The researchers stressed their finding does not upend the standard cosmological model for galaxy formation. Rather, the Red Monsters add a new wrinkle – the possibility that early galaxies could grow more quickly under specific conditions.
Future observations with JWST and the Atacama Large Millimetre Array in Chile will provide further insights into these supermassive Red Monsters and reveal larger samples of such galaxies, the researchers said.
The research team included more than three dozen astronomers from institutions in the United States, Switzerland, Denmark, the United Kingdom, France, the Netherlands, Japan, Australia and Spain.
