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Confirmation of JD1: The Faintest Galaxy Ever Seen in the Early Universe

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Fake color NIRCam image from Abell group 2744. Credit: alam (2023). DOI: 10.1038/s41586-023-05994-w

An international team of researchers led by astrophysicists at the University of California has confirmed the existence of the faintest galaxy ever seen in the early universe. The galaxy, called JD1, is one of the most distant galaxies identified so far, and is typical of the type of galaxy that burned through the fog of hydrogen atoms left over from the Big Bang, allowing light to penetrate the universe and shape it. to be what it is today.

The discovery was made using NASA’s James Webb Space Telescope, and the results were published in the journal alam.

The first billion years of the universe was a critical period in its evolution. After the Big Bang, about 13.8 billion years ago, the universe expanded and cooled enough to form hydrogen atoms. Hydrogen atoms absorb ultraviolet photons from young stars. However, it was not until the birth of the first stars and galaxies that the universe darkened and entered a period known as the cosmic dark ages.

The appearance of the first stars and galaxies several hundred million years later bathed the universe in energetic ultraviolet light that began to burn or ionize the hydrogen fog. This, in turn, allows photons to travel through space, making the universe transparent.

Determining the types of galaxies that dominated this era—dubbed the era of reionization—is a major goal of astronomy today, but until the Webb telescope was developed, scientists lacked the sensitive infrared instruments needed to study the first generations of galaxies.

“Most of the galaxies in JWST so far are rare bright galaxies and are not thought to represent young galaxies that inhabited the early universe,” said Guido Roberts-Borsani, a UCLA postdoctoral researcher and first author of the study. Thus, while important, they are not believed to be the main factor burning up all that hydrogen haze.

“Ultralight galaxies like JD1, on the other hand, are much more numerous, which is why we think they are more representative of galaxies that have undergone reionization, allowing ultraviolet light to travel unhindered through space and time.”

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Projection image of galaxy JD1 (inset), which lies behind the bright galaxy cluster Abell2744. Credits: Guido Roberts Borsani/UCLA); Original images: NASA, ESA, CSA, Swinburne University of Technology, University of Pittsburgh, STScI

JD1 is too dim and distant to study without a powerful telescope — and a helping hand from nature. JD1 lies behind a large group of nearby galaxies, called Abell 2744, whose combined gravitational forces bend and amplify the light from JD1, making it appear 13 times larger and brighter than it should be. The effect, known as gravitational lensing, is similar to the way a magnifying lens distorts and magnifies the light in its field of view; Without a gravity lens, the JD1 would likely have been missed.

The researchers used the Webb Telescope’s Near Infrared Spectrometer instrument, NIRSpec, to obtain the galaxy’s infrared light spectrum, which allowed them to accurately determine its age and distance from Earth, as well as the number of stars and the amount of dust and heavy debris. . the elements that make it up in its relatively short life.

The combination of the galaxy’s gravitational zoom and new images from Webb’s other near-infrared instrument, NIRCam, also allowed the team to study galaxy structure with unprecedented detail and resolution, uncovering the three main ridges of dust and gas that make up stars. . The team used the new data to trace JD1’s light back to its original source and shape, uncovering dense galaxies that are only a fraction of the size of ancient galaxies like the Milky Way, which is 13.6 billion years old.

Because light takes time to travel to Earth, JD1 looks like it did about 13.3 billion years ago, when the universe was only about 4% as old as it is today.

“Before the Webb telescope was turned on, just a year ago, we couldn’t even dream of confirming a galaxy so faint,” said Tommaso Trio, UCLA professor of physics and astronomy and author of both studies. “The combination of JWST and the amplifying power of gravitational lenses is revolutionary. We are currently rewriting the book about how galaxies formed and evolved in the immediate aftermath of the Big Bang.”

This study has been published in the journal alam.

further information:
Guido Roberts-Borsani et al, Properties of ultralight galaxies in the cosmic dark ages seen with JWST, alam (2023). DOI: 10.1038/s41586-023-05994-w

Journal information:
alam


2023-06-01 17:28:54
#Astrophysicists #confirm #faintest #galaxies #early #universe

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