Three recently identified "red monster" galaxies as seen in images from NASA's James Webb Space Telescope. (Credit: NASA/CSA/ESA, M. Xiao & P. A. Oesch (University of Geneva), G. Brammer (Niels Bohr Institute), Dawn JWST Archive)
This story was adapted from a version published by the University of Geneva. Read the original version here.
An international team including astrophysicist Erica Nelson from CU Boulder has identified three ultra-massive galaxies-nearly as massive as the Milky Way-already in place within the first billion years after the Big Bang.
This surprising discovery was made possible by the James Webb Space Telescope's FRESCO program, which uses the NIRCam/grism spectrograph to measure accurate distances and stellar masses of galaxies. The results indicate that the formation of stars in the early universe was far more efficient than previously thought, challenging existing galaxy formation models. The study, which was led by the University of Geneva in Switzerland, was published Nov. 13 in Nature.
"The thing that makes these massive galaxies so surprising is that they exist so early, when we don't think they should have had time to form," said Nelson, assistant professor in the Department of Astrophysical and Planetary Sciences. "It's like arriving home from work to check on your kitten and finding a cougar laying on your couch."
In the theoretical model favored by scientists, galaxies form gradually within large halos of dark matter. Dark matter halos capture gas (atoms and molecules) into gravitationally bound structures. Typically, only about 20% at most of this gas is converted into stars in galaxies. However, the new findings using NASA's Webb telescope challenge this view. They reveal that massive galaxies in the early universe may have been much more efficient in building stars than their later counterparts, growing much more rapidly than previously thought.
Nelson previously helped to identify several of the "red monsters" in a 2023 study. The new research takes an even closer look at several of these candidates-confirming that they are, in fact, as old and as large as they look.
''These results indicate that galaxies in the early universe could form stars with unexpected efficiency,'' said Mengyuan Xiao of the University of Geneva and lead author of the new study. ''As we study these galaxies in more depth, they will offer new insights into the conditions that shaped the universe's earliest epochs. The 'red monsters' are just the beginning of a new era in our exploration of the early universe.''
