A young galaxy with mature features challenges the theory of galaxy formation

An international team of scientists, including Filippo Fraternale from the University of Groningen, has discovered a distant young galaxy that looks much older than its age. In a short time, it is the second young galaxy that challenges the theory of galaxy formation. The researchers will publish their findings in the journal Science on Friday.

Astronomers have used the Atacama Large Millimeter / Sub-Millimeter Array (ALMA) dual satellite dishes to capture one of the clearest direct images ever of a distant young galaxy.

The young distant galaxy is called ALESS 073.1 and appears to have all of the features of more mature galaxies. The researchers saw, for example, a central bulge (bulge), a regularly rotating disc and possibly spiral arms. Lead author Federico Lilly (Cardiff University, UK). “This galaxy looks like an adult when it must be just a little kid.”

The galaxy is located at a distance of z = 5. That’s roughly equivalent to 12.5 billion light-years, but for such distant galaxies, researchers are no longer working in light years, because the distortion of space plays a role. Z = 5 means that astronomers are seeing the galaxy as it was 1.2 billion years after the Big Bang. So the galaxy is definitely younger than 1.2 billion years old.

Co-author Filippo Fraternale (University of Groningen) also discovered a much more mature galaxy than its August age suggests. “The galaxy that we discovered now is another 200 million years younger and contains more mature elements than the August Galaxy. It is becoming increasingly clear that our understanding of galaxy formation needs to be overhauled, as current models predict that these small galaxies must be very chaotic, but Our observations show the existence of a “mature” galaxy that is calm and regular.

The text continues after the ALMA image.ALMA satellite dishes. (C) ALMA / W. Garnier

More than ALMA
The ALMA consists of 66 satellite dishes spread over 16 kilometers on the Chajnantor Plateau in the Chilean Andes. It is a partnership between Europe, the United States, Canada, Japan, Taiwan, South Korea and Chile. The Netherlands has built three types of receivers for telescopes: Band 5, Band 9, and Band 2 (under development). The ALMA image is ten times as sharp as the Hubble Space Telescope.

The scientific article
A massive star bulge in a regularly rotating galaxy 1.2 billion years after the Big Bang. Written by: Federico Lilly, Enrico MD Teodoro, Filippo Fratternale, Alison WS Man, Zhi Yu Zhang, Carlos De Brick, Timothy A. Davis, Roberto Maiolino. Science, 12 februari 2021. Origineel (vanaf 12 februari), preprint (pdf).