'Red monsters' challenge what we know about the early universe

Scientists have uncovered an intriguing tale of galactic growth, featuring mysterious “red monsters” that are revealing new secrets of the young universe.

An international team of experts led by the University of Geneva (UNIGE) has discovered three ultra-massive galaxies – each almost as substantial as the Milky Way – that emerged within the first billion years following the Big Bang.

Theory of galaxy formation

This discovery surprised scientists because it challenges the popular theory of galaxy formation. According to current models, galaxies grow slowly within large halos of dark matter.

These halos, which are invisible structures, pull in gas that eventually forms stars. Traditionally, scientists believed only about 20% of this gas would turn into stars in these galaxies.

However, the findings from the UNIGE team show that these early massive galaxies were exceptionally efficient at creating stars. They produced stars much faster and in larger numbers than expected, growing at an extraordinary rate compared to galaxies that formed later.

This unexpected efficiency suggests that early galaxies grew in ways scientists hadn’t previously considered, prompting a rethink of galaxy formation theories.

The three “red monsters”

The James Webb Space Telescope’s FRESCO program made this remarkable discovery possible.

The beauty of the FRESCO program lies in its cutting-edge tool, the NIRCam/grism spectrograph, which enables accurate measurement of the distance and stellar masses of galaxies.

Thanks to the superior capabilities of JWST, astronomers have been able to study galaxies in the distant and early universe systematically – including massive and dust-obscured galaxies.

Upon examining the galaxies in the FRESCO survey, most galaxies conformed to existing models. Yet, the team found three galaxies that were surprisingly massive.

Due to their high dust content, which gives them a unique red appearance in JWST images, the giant galaxies are now known as the “red monsters.”

Unveiling the hidden red monsters

Dr. Mengyuan Xiao, the lead author of the study, is a postdoctoral researcher in the Department of Astronomy at UNIGE Faculty of Science.

Dr. Xiao joined forces with Dr. David Elbaz, director of research at CEA Paris-Saclay, to investigate the red monsters.

“Our findings are reshaping our understanding of galaxy formation in the early universe,” noted Dr. Xiao.

“The massive properties of these red monsters were hardly determined before JWST, as they are optically invisible due to dust attenuation,” said Dr. Elbaz.

Studying the growth of galaxies over time

Using the James Webb telescope, the researchers developed an innovative program which enables the systematic analysis of a complete sample of emission-line galaxies within the first billion years of cosmic history.

This program allowed the team to achieve precise distance estimates and reliable stellar mass measurements for the full galaxy sample.

Pascal Oesch is an associate professor in the Department of Astronomy at the UNIGE and principal investigator of the observation program.

“Our findings highlight the remarkable power of NIRCam/grism spectroscopy,” noted Oesch. “The instrument on board the space telescope allows us to identify and study the growth of galaxies over time, and to obtain a clearer picture of how stellar mass accumulates over the course of cosmic history.”

“Too many, too massive” galaxies

The discovery of these massive galaxies challenges existing ideas about how galaxies form.

The findings highlight the presence of an unexpectedly high number of large galaxies – “too many, too massive” galaxies – very early in the universe’s history.

This suggests that existing models may be missing certain processes or factors that allowed some galaxies to grow rapidly right after the Big Bang.

Future research directions

To understand these giant galaxies better, scientists will continue observing them with powerful instruments like JWST and ALMA.

These tools can offer more detailed views and help find more of these ultra-massive galaxies, deepening our understanding of galaxy formation in the early universe and potentially revising the models of cosmic evolution.

Future endeavors hold the promise of addressing lingering questions about the universe’s dark matter content, stellar formation processes, and the dynamic behavior of galaxies over cosmic time scales.

Significance of the red monsters

The discoveries with JWST have significantly contributed to our understanding of cosmic origins, particularly by offering new perspectives on the early universe.

These revelations challenge the existing paradigms of universe evolution, suggesting that even in the nascent stages following the Big Bang, there existed environments ripe for the rapid growth and formation of the red monsters.

“These results indicate that galaxies in the early universe could form stars with unexpected efficiency,” said Dr. Xiao.

“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.”

The study is published in the journal Nature.

Image Credit: NASA / CSA / ESA / M. Xiao & P. A. Oesch / G. Brammer / Dawn JWST Archive

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