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In May 2020, a new discovery was revealed by the ALMA Observatory in Chile of a huge spinning disk galaxy, the Wolfe Disk, the most distant spinning disk galaxy, observed when the universe was only 10% of its current age. , just 1.5 billion years after the Big Bang, challenging traditional galaxy formation patterns. In most galaxy formation hypotheses, galaxies begin to show a well-formed disk only about 6 billion years after the Big Bang.
The fact that astronomers found such a disk galaxy when the universe was only ten percent of its current age indicates that other growth processes must have dominated. The star formation rate in the Wolfe Disk (image above and below) was at least ten times that of our own Milky Way, making it one of the most productive galaxies in the early universe.
Survey of the ALMA Observatory
These growth processes were revealed by an international team of astronomers who studied 118 distant galaxies with the ALMA survey called ALPINE (the ALMA Large Program to Investigate C + at Early Times), by an international team of astronomers who have studied 118 galaxies. who are experiencing “growth accelerations”. “In the early universe showing that massive galaxies were already much more mature in the early universe than previously predicted.
Sudden spurts of growth
Most galaxies formed when the universe was still very young. Our galaxy, for example, probably 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 galaxies experienced a “growth spurt”. During this time, they built up most of their stellar mass and other properties, such as dust, heavy element content, and spiral disk shapes, which we see in galaxies today.
“The Big Bang Galaxy” – “Wolfe Disk” defies the previous assumptions
“To our surprise, many of them were much more mature than we expected,” said Andreas Faisst of the Infrared Processing and Analysis Center (IPAC) at the California Institute of Technology (Caltech). on the first and largest multi-wavelength survey of galaxies in the early universe. For a large sample of galaxies, the team collected measurements in optics (including Subaru, VISTA, Hubble, Keck and VLT), infrared (Spitzer) and radio (ALMA). Multiple wavelength studies are needed to get a complete picture of how galaxies are formed.
“Primordial for mature”
Galaxies are considered more “mature” than “primordial” when they contain a significant amount of dust and heavy elements. “We didn’t expect to see so much dust and heavy elements in these distant galaxies,” Faisst said. Dust and heavy elements (defined by astronomers as all elements heavier than hydrogen and helium) are considered a byproduct of dying stars. But galaxies in the early universe haven’t had much time to build stars yet, so astronomers don’t expect to see a lot of dust or heavy elements there too.
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“From previous studies, we learned that these young galaxies are low in dust,” said Daniel Schaerer of the University of Geneva in Switzerland. “However, we find about 20 percent of the galaxies that assembled during this first epoch are already very dusty, and a significant fraction of the ultraviolet light from newborn stars is already hidden by this dust,” he added.
“Train Wrecks vs Orderly Spirals”
Many of the galaxies were also considered relatively adult because they displayed diversity in their structures, including early signs of spin-supported disks, which could later lead to galaxies with a spiral structure as seen in galaxies such as our Milky Modo. Astronomers generally expect galaxies in the early universe to look like wrecked trains because they often collide.
“We see many galaxies colliding, but we also see a number of them rotating in an orderly fashion with no signs of collision,” said John Silverman of the Kavli Institute for the Physics and Mathematics of the Universe in Japan.
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Disconcerting: MAMBO-9 and the Wolfe record
ALMA has already identified very distant galaxies, such as MAMBO-9 (a very dusty galaxy, image below) and the Wolfe disk. But it was hard to tell if these findings were unique or if there were more galaxies like them out there. ALPINE is the first investigation that allowed astronomers to study a significant number of galaxies in the early universe and shows that they could evolve faster than expected. But scientists still don’t understand how these galaxies grew so fast and why some of them already have spinning discs.
ALMA’s observations were crucial to this research because the radio telescope can see star formation hidden by dust and track the movement of gas emitted by star-forming regions. Investigations of galaxies in the early universe commonly use optical and infrared telescopes. These allow measurement of unobscured star formation and star masses. However, these telescopes have difficulty measuring the dust-obscured regions where stars form or the movements of gas in these galaxies. And sometimes they don’t see a galaxy at all.
Hubble dark galaxies
“With ALMA we have discovered some distant galaxies for the first time. We call them Hubble-dark because they can’t even be detected with the Hubble telescope, “said Lin Yan of Caltech.
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“We want to see exactly where the dust is and how the gas moves. We also want to compare dusty galaxies with others at the same distance and understand if there could be something special in their environments “, added Paolo Cassata of the University of Padua in Italy, previously at the Universidad de Valparaíso in Chile, on wanting to target it ALMA. on individual galaxies for a longer time.
The Daily Galaxy, Max Goldberg, via ALMA Observatory and NRAO
Image credit: ALMA radio image of the Wolfe record, seen when the universe was only ten percent of its current age. ALMA (ESO / NAOJ / NRAO), M. Neeleman; NRAO / AUI / NSF, S. Dagnello
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