The bright galaxies found by the James Webb Space Telescope (JWST) in the very early universe could be the product of bursts of massive star formation — and it’s likely that this fact renders the galaxies more luminous than expected for the era in which they exist. This is the conclusion drawn by researchers who used computer simulations to model how these galaxies formed and began producing stars.
When the JWST began science operations in the summer of 2022, its deep observations of the universe quickly began turning up high-redshift galaxies. These are galaxies that seemed to have existed earlier in the universe than astronomers had ever seen before. In fact, the galaxies, which were seen as they were when the universe was less than 400 million years old, appeared more luminous than what the standard model of cosmology predicts for the era. This led to claims that the standard model —which depicts galaxies starting off small and then growing hierarchically through mergers driven by filaments and haloes of dark matter in the cosmic web — must be wrong.
“The discovery of these galaxies was a big surprise because they were substantially brighter than anticipated,” Claude-André Faucher-Giguère of Northwestern University said in a statement
. “Typically, a galaxy is bright because it’s big, but since these galaxies formed at cosmic dawn, not enough time has passed since the Big Bang
. How could these massive galaxies assemble so quickly?”
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Faucher-Giguère is a member of a team led by Guochao Sun of Caltech, who together are performing simulations of how the first galaxies formed. They found that rather than being big, the galaxies observed by the JWST are luminous because they are seen during a time when they underwent a frenzy of star formation. The simulations succeed in not only modeling the luminosity of the galaxies, but also their abundance, both of…