Galaxies in the very early universe were surprisingly mature

October 30, 2020

Massive galaxies were already much more mature in the early universe than previously expected. This is the conclusion of an international team of astronomers who studied distant galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA). The result is now published by the National Radio Astronomy Observatory. Researchers from the The Cosmic Dawn Center at the Niels Bohr Institute, University of Copenhagen participated in the project, and Seiji Fujimoto, postdoc, explains the objective like this: "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".

Unexpected maturity of galaxies in a very young universe Most galaxies formed when the universe was still very young. Our own galaxy, the Milky Way, likely started forming 13.6 billion years ago, in our 13.8 billion-year-old universe. When the universe was only ten percent of its current age (1-1.5 billion years after the Big Bang), most of the galaxies experienced a "growth spurt". During this time, they built up most of their stellar mass and other properties, and the amount of dust, metal content, and their spiral-disk shapes are what we see in today's galaxies. Therefore, if we want to learn how galaxies like our Milky Way formed, it is important to study this epoch.

ALMA obtained a more coherent picture of the population of galaxies in the ALPINE survey Galaxies are considered more mature when they contain a significant amount of dust and heavy elements (metals), as dust and metals are a by-product of dying stars. But galaxies in the early universe have not had much time to build stars yet, let alone see the ending of their lifespan, so the team of astronomers didn't expect to see much dust or metals. Nevertheless, this turned out to be the case, and it even proved to be more "the order of the day" than a special case in the population of galaxies observed in the ALPINE project (the ALMA Large Program to Investigate C+ at Early Times). Seiji Fujimoto explains the significance of this: "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".

New and surprising discoveries were also made by ALMA in the process ALMA is not only able to obtain an image of each galaxy, but can also see how the metal gas moves in the individual galaxies. Because forming-phase galaxies are expected to have highly disordered motions, the metal gas motion tells us something about the matureness of the galaxies. It turned out that while many of the galaxies are colliding, the team also found that a number of them are rotating in an orderly fashion with no signs of collisions. Surprisingly, the team even discovered a galaxy surrounded by a huge rotating metal gas that far exceeds the stellar distribution. This probably means that the metal gas was pushed away from the galaxy in distorted motions by supernova explosions or energetic jets and radiation from supermassive black holes, but it formed the ordered rotating disk after a sufficient time.

What can be considered "normal" in the early Universe? These results allow for the survey's conclusions on what the normality of the observed galaxies were. Seiji Fujimoto explains the quest for the standard condition like this: "This time we studied the galaxies based on the metal and dust information, something we haven't been able to acquire from previous observations. Based on the comprehensive perspective of the galaxies, we focused on obtaining what we could call the normal picture in the early universe, which automatically defines what is unusual at the same time and allows us to identify unique objects. The normal picture will help us to much better determine the evolution of our Universe. 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 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".

The astronomers now wish to point ALMA at individual galaxies for a longer time to answer further questions, such as where the dust and metals are and how they move around. A comparison of these properties between the dust/metal-rich and -poor galaxies at similar distances may answer if the unexpectedly mature galaxies are formed with special circumstances in their environments.

University of Copenhagen

Related Astronomers Articles from Brightsurf:

Astronomers are bulging with data
For the first time, over 250 million stars in our galaxy's bulge have been surveyed in near-ultraviolet, optical, and near-infrared light, opening the door for astronomers to reexamine key questions about the Milky Way's formation and history.

Astronomers capture a pulsar 'powering up'
A Monash-University-led collaboration has, for the first time, observed the full, 12-day process of material spiralling into a distant neutron star, triggering an X-ray outburst thousands of times brighter than our Sun.

Astronomers discover new class of cosmic explosions
Analysis of two cosmic explosions indicates to astronomers that the pair, along with a puzzling blast from 2018, constitute a new type of event, with similarities to some supernovae and gamma-ray bursts, but also with significant differences.

Astronomers discover planet that never was
What was thought to be an exoplanet in a nearby star system likely never existed in the first place, according to University of Arizona astronomers.

Canadian astronomers determine Earth's fingerprint
Two McGill University astronomers have assembled a 'fingerprint' for Earth, which could be used to identify a planet beyond our Solar System capable of supporting life.

Astronomers help wage war on cancer
Techniques developed by astronomers could help in the fight against breast and skin cancer.

Astronomers make history in a split second
In a world first, an Australian-led international team of astronomers has determined the precise location of a powerful one-off burst of cosmic radio waves.

Astronomers witness galaxy megamerger
Using the Atacama Large Millimeter/submillimeter Array (ALMA), an international team of scientists has uncovered a startlingly dense concentration of 14 galaxies that are poised to merge, forming the core of what will eventually become a colossal galaxy cluster.

Astronomers discover a star that would not die
An international team of astronomers has made a bizarre discovery; a star that refuses to stop shining.

Astronomers spun up by galaxy-shape finding
For the first time astronomers have measured how a galaxy's spin affects its shape -- something scientists have tried to do for 90 years -- using a sample of 845 galaxies.

Read More: Astronomers News and Astronomers Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to