Sunday, June 26, 2022

Astronomers find early cosmic galaxies may be larger than previously thought

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Immature galaxies in the very early Universe may be larger than they first appear. That’s an implication of the results, presented Tuesday at the 240thth Meeting of the American Astronomical Society in Pasadena, California.

Using radio astronomy rather than visible or infrared telescopes, the researchers observed significant outflows of hot gas from the center and cold gas in the outer regions of young galaxy A1689-zD1, which could help astronomers better understand how galaxies evolve and during them become more structured mature.

The results to be published in a future issue of The Astrophysical Journalalso demonstrate the value of using radio astronomy to study galaxies previously discovered by instruments such as the Hubble Space Telescope.

A1689-zD1 appears as a juvenile, star-forming galaxy slightly less massive than our own Milky Way and some 13 billion light-years distant in the constellation Virgo. That distance means the A1689-zD1 observed by astronomers appears to have existed just 700 million years after the Big Bang, taking billions of years for its light to reach us.

A1689-zD1 was discovered in 2015 using the Hubble Space Telescope and the Spitzer Space Telescope, along with a technique known as gravitational lensing, which uses the gravity of a massive galaxy cluster in the foreground of a telescope’s field of view to bend the galaxy and magnify the light of a more distant one galaxy in the background.

The new research was conducted with the Atacama Large Millimeter/submillimeter Array, ALMA, radio telescope in northern Chile. The observations revealed that A1689-zD1 possessed a halo of cold carbon gas and also produced hot outflows of material from its center, typically associated with supermassive black holes at the centers of some galaxies.

Both the outflows and the halo of cold gas are not typical of such young galaxies, at least from what has been observed so far. However, the new observations suggest that astronomers may need to change what they consider normal for these early cosmic structures.

“We have seen these types of extended gas halo emissions from galaxies that formed later in the Universe, but seeing them in such an early galaxy means that this type of behavior is evident even in the humbler galaxies that make up most of the stars in the universe universe formed, universal is early universe,” said Darach Watson, associate professor at the Niels Bohr Institute at the University of Copenhagen and co-author of the study, in a statement. “Understanding how these processes occurred in such a young galaxy is crucial to understanding how star formation occurs in the early Universe.”

The gas halo observed in the new observations also suggests that early galaxies may be larger than previous optical and infrared observations suggested, according to Seiji Fujimoto, a postdoc at the Niels Bohr Institute.

“The emission of the carbon gas in A1689-zD1 is much more widespread than what was observed with the Hubble Space Telescope, and this could mean that early galaxies are not as small as they appear,” said Dr. Fujimoto in a statement. “If early galaxies are indeed larger than we previously thought, this would have a major impact on the theory of galaxy formation and evolution in the early Universe.”

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