ALMA Spots Assemblage of Galaxies in the Early Universe

First Posted: Jul 22, 2015 10:52 AM EDT

A few hundred million years after the Big Bang, the first galaxies started to form within a fog of hydrogen gas. As more bright bodies began to form, though, they cleared away the mist. Now, scientists have learned a bit more about the very first galaxies with the help of ALMA.

In this latest study, the researchers used ALMA to look at galaxies that were known to be seen only about 800 million years after the Big Bang. The astronomers didn't focus on the light from stars, but instead focused on the faint glow of ionized carbon coming from the clouds of gas from which the stars were forming.

One of the galaxies, called BDF 3299, actually gave off a faint but clear signal from glowing carbon. However, this glow wasn't coming from the center of the galaxy. Instead, it was coming from one side.

"This is the most distant detection ever of this kind of emission from a 'normal galaxy, seen less than one billion years after the Big Bang," said Andrea Ferrara, co-author of the new study, in a news release. "It gives us the opportunity to watch the build-up of the first galaxies. For the first time we are seeing early galaxies not merely as tiny blobs, but as objects with internal structure!"

The astronomers believe that the off-center location of the glow is because the central clouds are being disrupted by the harsh environment created by the newly formed stars while the carbon glow is tracing fresh, cold gas that is being accreted from the intergalactic medium.

"We have been trying to understand the interstellar medium and the formation of the reionization sources for many years," said Ferrara. "Finally to be able to test predictions and hypotheses on real data from ALMA is an exciting moment and opens up a new set of questions. This type of observation will clarify many of the thorny problems we have with the formation of the first stars and galaxies in the universe."

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.