Researchers from DAWN discover mature galaxies in the very early universe

05. November 2020

A new study shows that large galaxies were much more mature in the early universe than previously assumed. The distant galaxies have been studied by a team of researchers from the Cosmic Dawn Center (DAWN), a DNRF Center of Excellence at the Space Division at the Technical University of Denmark and the Niels Bohr Institute at the University of Copenhagen, along with a team of international astronomers with data from the Atacama Large Millimeter/submillimeter Array (ALMA).

An artist's illustration of a rotating and dusty distant galaxy
An artist’s illustration of a rotating and dusty distant galaxy Photo: B. Saxton NRAO/AUI/NSF, ESO, NASA/STScI; NAOJ/Subaru

The majority of galaxies were formed when the universe was still very young. Up until now, it was thought that the big galaxies were not mature in the very early universe. But a new study from a team of researchers from the Cosmic Dawn Center (DAWN) at the Space Division at the Technical University of Denmark and the Niels Bohr Institute at the University of Copenhagen and a team of international astronomers with data from the Atacama Large Millimeter/submillimeter Array (ALMA), now shows otherwise.

“We performed the first large multi-wavelength survey of distant galaxies, in order to understand the initial phase of galaxy formation and evolution in the universe. We didn’t expect to find such mature galaxies, and this new information allows us to now paint a more coherent picture of the average condition in the early universe,” said Seiji Fujimoto from the DNRF’s Cosmic Dawn Center (DAWN) at the Niels Bohr Institute at the University of Copenhagen.

Immense maturity in galaxies in the early universe

In the period 1–1.5 billion years after the Big Bang a growth spurt occurred whereby the galaxies in this period built up most of their properties and stellar mass. Some of the things formed during this stage were the amount of dust, the metal content, and their spiral-disk shapes. When researchers want to study the big galaxies, including our own Milky Way, it is  this period at which they need to take a closer look.

Galaxies are considered mature when they contain a significant amount of dust and heavy elements in the form of metals, as dust and metals are a by-product of dying stars. The team of astronomers did not expect to find a large amount of dust and metals, as the galaxies from the early universe did not have much time to build stars, which meant they could not have had a large amount of death stars. Therefore,  finding a large amount of dust and metal was a spectacular discovery, along with the results that this was “the order of the day” in the galaxies.

“Sometimes, if the entire galaxy we wish to observe is obscured by dust, we can’t get the information we’re after using optical telescopes – telescopes that observe using visible light. But with ALMA, a radio telescope observing via invisible longer wavelengths, we are able to see through the ‘veil of dust and metal gas,’” said Fujimoto.

New understanding of the “order of the day” in the large galaxies

The motion of metal gas tells us something about the maturity of the galaxies, as the galaxies in the formation phase are expected to have highly disordered motions. A team of astronomers discovered a galaxy surrounded by a huge rotating metal gas that far exceeds the stellar distribution, which probably means that the metal gas was pushed away by distorted motions from energetic jets and radiation or supernova explosions.

This new result from the study means that it is possible to conclude what the “order of the day” was in the observed galaxies. The next step is to figure out if the unexpected mature galaxies were formed because of special circumstances in their environments.

“In fact, cosmological theorists will need this new information to build up a theoretically more precise picture of the development of the universe. Furthermore, we may learn of new cosmological events or physical mechanisms in galaxies through the objects that are out of the ordinary. This research will contribute to our fundamental understanding of the universe we are part of,” said Fujimoto.

Read the scientific article from the National Radio Astronomy Observatory here

More information about the mature galaxies in the early universe can be found at the University of Copenhagen here