An international team from the University of Geneva (UNIGE) has discovered three ultra-massive galaxies that are nearly as massive as the Milky Way, existing within the first billion years following the Big Bang. This unexpected finding was made possible through the James Webb Space Telescope’s FRESCO program, which employs the NIRCam/grism spectrograph to accurately gauge distances and stellar masses of galaxies. The results suggest that stars formed in the early Universe much more efficiently than earlier models had predicted, calling into question established theories of galaxy formation. This research is published in Nature.
According to the prevailing scientific model, galaxies gradually form within vast dark matter halos. These halos draw in gas (composed of atoms and molecules), leading to gravitationally bound structures. Typically, only about 20% of this gas is converted into stars within galaxies. However, the new discoveries from the UNIGE team, in collaboration with NASA’s James Webb Space Telescope (JWST), challenge this traditional understanding. They suggest that massive galaxies in the early Universe may have been considerably more adept at star formation than those formed later, growing at rates much faster than previously assumed.
Discovery of “Red Monsters”
The JWST’s extraordinary capabilities have enabled astronomers to explore galaxies from the extremely distant early Universe, shedding light on massive and dust-covered galaxies. When examining the galaxies in the FRESCO survey, researchers found that, while most galaxies conformed to existing theories, there were also three unexpectedly massive galaxies with stellar masses similar to the current Milky Way. These galaxies are generating stars nearly twice as efficiently as less massive galaxies and those that formed later. Due to their high dust content, which gives them a distinctive red hue in JWST images, they have been dubbed the “Red Monsters.”
”Our discoveries are transforming our understanding of galaxy formation during the early Universe,” states Dr. Mengyuan Xiao, the study’s lead author and a postdoctoral researcher in the Department of Astronomy at UNIGE. ”Before JWST, the significant characteristics of these ‘Red Monsters’ were difficult to ascertain, as they were visually obscured by dust,” explains Dr. David Elbaz, research director at CEA Paris-Saclay.
A Milestone in Galaxy Observations
The international research team has created a new program with the JWST aimed at systematically analyzing a complete sample of emission-line galaxies from the first billion years of cosmic history. This innovative approach has allowed the team to obtain precise distances and accurate measurements of stellar mass for the entire galaxy sample.
”Our findings underscore the exceptional capabilities of NIRCam/grism spectroscopy,” says Pascal Oesch, associate professor in the Department of Astronomy at UNIGE and the principal investigator of this observational program. ”The space telescope’s instruments enable us to identify and track the growth of galaxies over time and develop a clearer understanding of how stellar mass accumulates throughout cosmic history.”
”Too Many, Too Massive” Galaxies in the Early Universe
While these results do not contradict the standard cosmological model, they introduce new questions regarding galaxy formation theories, particularly the concern of “too many, too massive” galaxies appearing in the early Universe. Current models may need to incorporate distinctive processes that facilitated certain early massive galaxies in attaining such efficient star formation and thus developing at remarkable speeds in the early Universe. Future observations with JWST and the Atacama Large Millimeter Array (ALMA) will further explore these ultra-massive “Red Monsters” and uncover a larger variety of such galaxies.
”These findings indicate that galaxies in the early Universe could generate stars with surprising efficiency,” concludes Dr. Mengyuan Xiao. ”As we delve deeper into studying these galaxies, they will provide new perspectives on the conditions that influenced the Universe’s earliest periods. The ‘Red Monsters’ are just the start of a new chapter in our investigation of the early Universe.”
