Galaxies in the previous universe could be “much bigger than we thought”

Galaxies in the previous universe could be “much bigger than we thought”

This artist's conception illustrates the previously unknown complexity of the young galaxy, A1689-zD1.  (ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF))

This artist’s conception illustrates the previously unknown complexity of the young galaxy, A1689-zD1. (ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF))

Immature galaxies in the early universe may be larger than they appear at first glance. This is an implication of the findings presented in 240º American Astronomical Society meeting 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 the young galaxy A1689-zD1 that could help astronomers better understand how galaxies evolve and become more structured over time. as they develop. mature.

The findings, which will be published in an upcoming issue of The Astrophysical Journalalso show the value of using radio astronomy to study galaxies previously discovered by instruments such as the Hubble Space Telescope.

A1689-zD1 appears as a young star-forming galaxy slightly less massive than our Milky Way, and about 13 billion light-years away from us in the constellation Virgo. That distance means astronomers observe A1689-zD1 appears as it existed just 700 million years after the Big Bang, its light took billions of years 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 cluster of galaxies in the foreground of a telescope’s field of view to bend and magnify the light of a more distant galaxy in the background.

The new survey was carried out using the Atacama Large Millimeter/submillimeter Array, ALMA, radio telescope in northern Chile. The observations found that A1689-zD1 had a halo of cold carbon dioxide and also generated hot outflows of material from its center, something 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 as far as existing observations go. But the new observations suggest that astronomers may need to change what they consider normal for these early cosmic structures.

“We have seen this kind of halo emission from extended gas from galaxies that formed later in the Universe, but seeing it in such a primitive galaxy means that this kind of behavior is universal even in the more modest galaxies that formed most of the stars in the world. Universe. primitive universe,” Darach Watson, an associate professor at the Niels Bohr Institute at the University of Copenhagen and co-author of the research, said in a statement.

“Understanding how these processes occurred in such a young galaxy is critical to understanding how star formation happens in the early Universe.”

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

“The emission of carbon dioxide in A1689-zD1 is much more extensive than that observed with the Hubble Space Telescope, and this could mean that the first galaxies are not as small as they appear,” Fujimoto said in a statement.

“If, in fact, the first galaxies are larger than we previously believed, this would have a big impact on the theory of galaxy formation and evolution in the early Universe.”

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