James Webb helps to identify most distant galaxies confirmed to date
A study by an international team of astronomers has identified a group of the earliest galaxies confirmed to date. The team based its findings on the data processed by Nasa's James Webb Space Telescope (JWST). The galaxies are estimated to be less than 400 million years after the big bang, and light from these sources has taken roughly 13.4 billion years to reach the Earth's atmosphere.
“For the first time, we have discovered galaxies only 350 million years after the big bang, and we can be absolutely confident of their fantastic distances,” said Brant Robertson, the co-author of the study from the University of California Santa Cruz. The area in and around the Hubble Space Telescope’s Ultra Deep Field was the focus area in the first round of the Webb Advanced Deep Extragalactic Survey (JADES).
Astronomer and co-author, Emma Curtis-Lake from the University of Hertfordshire in the United Kingdom said that "it was crucial to prove that these galaxies do, indeed, inhabit the early universe. It’s very possible for closer galaxies to masquerade as very distant galaxies.”
How the results were achieved
The team utilized the JWST's Near-Infrared Camera and the Near-Infrared Spectrograph to observe different infrared wavelength ranges and derived a precise measurement of each galaxy’s redshift. Researchers could distinguish such early galaxies from their multi-wavelength colors as the light gets stretched in wavelength as the universe expands. This is known as cosmological redshift, with the increasing values equating to a larger distance.
Researchers studied light from 250 faintest galaxies and found that four of the galaxies studied are particularly special. "The results provided spectroscopic confirmation that these four galaxies lie at redshifts above 10, including two at redshift 13. This corresponds to a time when the universe was approximately 330 million years old," according to a release.
“Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see! It is a tremendously exciting achievement for the mission, said Curtis-Lake.”
The second stage of JADES will continue in 2023 with a detailed study of the Hubble Deep Field, and then "return to the Ultra Deep Field for another round of deep imaging and spectroscopy."
Finding and characterising the first galaxies that illuminated the early Universe at cosmic dawn is pivotal to understand the physical conditions and the processes that led to the formation of the first stars. In the first few months of operations, imaging from the James Webb Space Telescope (JWST) has been used to identify tens of candidates of galaxies at redshift (z) greater than 10 [2–9], less than 450 million years after the Big Bang. However, none of such candidates has yet been confirmed spectroscopically, leaving open the possibility that they are actually low-redshift interlopers. Here we present spectroscopic confirmation and analysis of four galaxies unambiguously detected at redshift 10.3≤z≤13.2, previously selected from NIRCam imaging. The spectra reveal that these primeval galaxies are extremely metal poor, have masses between 107 and a few times 108 solar masses, and young ages. Springer Nature 2021 LATEX template 4 NIRSpec z > 10 The damping wings that shape the continuum close to the Lyman edge are consistent with a fully neutral intergalactic medium at this epoch. These findings demonstrate the rapid emergence of the first generations of galaxies at cosmic dawn.
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