New observations that contribute to the theory of galaxy formation have been published by astronomers at the Cosmic Dawn Center using the James Webb Space Telescope.
A small group of galaxies seen about 13 billion years ago that may be in the process of forming a giant galaxy. The colors are made up of three different infrared colors. The white horizontal bar marks a scale of approximately 20,000 light years. Image credit: Shuowen Jin et al. (2023).
Researchers have observed groups of smaller galaxies in the process of forming larger galaxies. They think they are probably the progenitors of giant galaxies like the Milky Way. This breakthrough confirms our current understanding of how galaxies develop.
According to current knowledge, galaxies develop hierarchically, initially consisting of small systems that developed in the very early universe, which then merge to build larger systems. This is the main theory backed by computer simulations and validated by observations of galaxies during many epochs of the history of the universe.
To think about assembling the first system, we need to go as far back as possible. However, the evidence for these systems is very small and faint, and their detection requires sophisticated techniques.
A new study has detected early precursors to what probably evolved into giant galaxies today. This small group of galaxies, called CGG-z5, was discovered by the James Webb Space Telescope’s observing program known as ‘CEERS’ when the universe was only 1.1 billion years old, just 8% of its current age. rice field.
CGG-z5 was discovered with the help of the code GalCluster, written by Nikolaj Sillassen, a master’s student at the Cosmic Dawn Center (DAWN).
During my research, I developed software to detect this type of structure and applied it to data from the CEERS program.. It’s great to see how useful my code is.
Nikolaj Silassen, MSc Student, Cosmic Dawn Center
Silassen had already discovered similar but closer groups while testing the software.
Impossible without James Webb
The brightest member of the galaxy group was previously discovered with the Hubble Space Telescope. However, the CEERS program has found a new small member.
“Other members of the group are small and faint. Without the sensitivity and spatial resolution of James Webb, we would not be able to detect them.explains Shuowen Jin, Marie Curie Fellow of the Cosmic Dawn Center (DAWN) and lead author of the current study.
What the exact “future” will be for the galaxy group named CGG-z5 is, of course, unknown. Instead of developing a single galaxy, the group may have progressed into a giant cluster of galaxies.
help from computer simulation
High-precision observations by spectroscopic analysis are required to distinguish between such scenarios.
To better understand the nature and evolution of CGG-z5, we searched for similar structures in large-scale hydrodynamic simulations..
Aswin Vijiayan, Postdoctoral Fellow, Cosmic Dawn Center
Vijiayan added:We found 14 structures that closely match the observed physical properties of the group CGG-z5 and tracked the evolution of these structures over time in simulations, from the early Universe to the present epoch. . ”
Vijiayan performed simulation analysis in this study.
Although the exact evolution of the 14 structures appears to be diverse, they all shared the same fate. About 500 million to 1 billion years later, they merged and developed individual galaxies, which by the time the universe was half of its present age, had a mass comparable to that of the Milky Way.
Given the simulation predictions, it is therefore tempting to speculate that the CGG-z5 system may have followed a similar evolutionary path, capturing the process of small galaxies merging into one giant galaxy..
Shuowen Jin, Lead Study Author, Cosmic Dawn Center, Marie Curie Fellow
“Interestingly, the number of early groups like CGG-z5 in a given space is similar to the number of massive galaxies in the later space age.. This makes the merger group attractive as the main progenitor of massive galaxies in later erasconcludes Georgios Magdis, an associate professor at DAWN who participated in the study.
Journal references
Jin, S. others(2022) Active massive galaxy formation at z~5 in the JWST. Astronomy and Astrophysics. doi.org/10.1051/0004-6361/202245724.
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