Webb telescope catches early galaxy formation in action

Astronomers at the Cosmic Dawn Center have revealed the nature of the densest regions of galaxies seen with the James Webb Space Telescope in the early universe. They find that it is likely the progenitor of large Milky Way-like galaxies seen when they are still clustered together from smaller galaxies. This discovery supports our understanding of how galaxies form.

According to our current understanding of structure formation in the universe, galaxies form hierarchically, with smaller structures forming first. early universe, later merged to build a larger structure. This is a prediction of theory, computer simulationverified by observations of galaxies from different epochs of cosmic history.

Observing the first structure assembled requires looking as far back as possible. However, both of these sources are very small and weak, and their detection requires advanced technology.

A new study today has detected early precursors of what likely evolved into giant Milky Way-sized galaxies. It was discovered through an observation program called , and is seen when the universe was only 1.1 billion years old, 8% of its current age.

CGG-z5 was discovered using the code GalCluster, written by Nikolaj Sillassen, a master’s student at the Cosmic Dawn Center (DAWN).

“We developed software during our research to detect this kind of structure and applied it to data from the CEERS program,” says Nikolaj Sillassen. I already found a similar but closer group while testing the software.

“It’s nice to see how useful my code is.”

Impossible without James Webb

The brightest member of the galaxy group was previously discovered with the Hubble Space Telescope. However, the CEERS program revealed a small new member.

“The other members of the group are both small and faint. We would not have been able to detect them without the sensitivity and spatial resolution of James Webb.) and lead author of the current study.”

What the “future” of galaxy group CGG-z5 will be, of course, is unknown. Rather than forming a single galaxy, this group may later evolve into a large cluster of galaxies. Yet another possibility is that the members are actually part of a filamentary structure that happens to be visible end-to-end, instead of being as dense as it seems.

help from computer simulation

Distinguishing between these scenarios requires more precise observations, including more time-consuming spectroscopy. But in the meantime, help is available from computer simulations.

“We looked for similar structures in large-scale hydrodynamic simulations to better understand the nature and evolution of CGG-z5.” simulation Analysis in research. “We found 14 structures to be in close agreement. physical properties We traced the evolution of these structures over time in simulations of our observed group CGG-z5 from the early Universe to the present epoch.

Although the exact evolution of these 14 structures differs, they all share the same fate. universe It is half the age of today and has a mass comparable to our own Milky Way.

“Given the simulation predictions, it’s tempting to speculate that the CGG-z5 system followed a similar evolutionary path, capturing the process of small galaxies merging into one giant galaxy,” says Shuowen Jin. says.

“Interestingly, the number of these early groups, like CGG-z5, in a given space is similar to the number of massive galaxies in the later space age,” said an associate professor at DAWN who participated in the study. Georgios Magdis said. “This makes group merging attractive as a large primary ancestor. galaxy in later times. ”

The research is published in the journal Astronomy and Astrophysics.