Actively forming galaxies in the early universe feed on cold gas – Eurasia Review

Researchers analyzing data from NASA’s James Webb Space Telescope have identified three galaxies that may have been actively forming when the universe was only 400 to 600 million years old. Webb’s data shows that these galaxies are surrounded by gas that researchers suspect is almost entirely hydrogen and helium, the first elements to exist in the cosmos. Webb’s instruments are so sensitive that they were able to detect an unusual amount of dense gas surrounding these galaxies. This gas will likely eventually fuel the formation of new stars in galaxies.

“These galaxies are like shimmering islands in an otherwise neutral and opaque sea of ​​gas,” explained Kasper Heintz, lead author and assistant professor of astrophysics at the Cosmic Dawn Center (DAWN) at the University of Copenhagen in Denmark. “Without Webb, we would not be able to observe these very first galaxies, let alone learn as much about their formation.”

“We are moving away from an image of galaxies as isolated ecosystems. At this point in the history of the universe, galaxies are all intimately linked to the intergalactic medium with its filaments and pristine gas structures,” added Simone Nielsen, co-author and doctoral student also based at DAWN.

In Webb’s images, galaxies look like faint red spots, so additional data, called spectra, were key to the team’s conclusions. These spectra show that the light from these galaxies is absorbed by large amounts of neutral hydrogen. “The gas must be very widespread and cover a very large part of the galaxy,” said Darach Watson, co-author and professor at DAWN. “This suggests that we are seeing the assembly of neutral hydrogen in galaxies. This gas will continue to cool, clump together, and form new stars.

The universe was a very different place several hundred million years after the Big Bang, during a period known as the Reionization Era. The gas between stars and galaxies was largely opaque. Gas in the universe did not become fully transparent until about 1 billion years after the big bang. Stars in galaxies helped heat and ionize the gas around them, eventually making it completely transparent.

By matching Webb’s data with models of star formation, the researchers also discovered that these galaxies primarily harbor populations of young stars. “The fact that we are observing large reservoirs of gas also suggests that galaxies have not yet had enough time to form most of their stars,” Watson added.

This is just the beginning

Webb not only meets the mission goals that motivated its development and launch, he exceeds them. “Images and data from these distant galaxies were impossible to obtain before Webb,” explained Gabriel Brammer, co-author and associate professor at DAWN. “Plus, we had a good idea of ​​what we were going to find when we first saw the data – we were almost making visual discoveries. »

There are still many more questions to answer. Where exactly is the gas? How much is near the centers of galaxies – or at their outskirts? Is the gas virgin or already populated with heavier elements? Important research lies ahead. “The next step is to create large statistical samples of galaxies and quantify in detail the prevalence and importance of their features,” Heintz said.