Age of ancient galaxy discovered by Webb, confirmed by ALMA

Since the launch of the James Webb Space Telescope in December 2021, astronomers and the public have been excited about how powerful this new instrument is and how it could see some of the most distant galaxies ever observed. However, because it is cutting edge research, some of these early results have been controversial as astronomers have been working to find out how accurate the data is due to issues such as how to calibrate the instruments.

Another way to verify the results is to look for supporting evidence from other tools, such as B. Recent work with the Atacama Large Millimeter/submillimeter Array or ALMA, a ground-based array of telescopes in Chile, which has confirmed the age of a very distant galaxy with evidence of oxygen.

A distant galaxy identified by JWST, GHZ2/GLASS-z12.
The ALMA radio telescope array has determined the exact cosmic age of a distant JWST-identified galaxy, GHZ2/GLASS-z12, to be 367 million years after the Big Bang. ALMA’s deep spectroscopic observations revealed a spectral emission line associated with ionized oxygen near the galaxy that has been shifted in its observed frequency due to the expansion of the universe since the line was emitted. This observation confirms the JWST’s ability to record distances and heralds a leap in our ability to understand the formation of the earliest galaxies in the Universe. NASA/ESA/CSA/T Treu, UCLA/NAOJ/T Bakx, Nagoya U.

A group of researchers from Nagoya University and the National Astronomical Observatory of Japan studied a galaxy called GHZ2 or GLASS-z12, first identified in the James Webb GLASS survey. To see if the galaxy was really as old as it appeared to be, the researchers used ALMA to perform a technique called spectroscopy, which breaks up the light coming from the target into different wavelengths. This shows which wavelengths are missing because they have been absorbed by a specific element – oxygen in this case.

The research examined the emission line of oxygen and confirmed its redshift, which refers to the shift of light from a distant target to the red end of the spectrum due to the expansion of the universe. This allowed them to confirm that the GLASS-Z12 galaxy is extremely old, dating back 367 million years after the Big Bang.

“The first images from the James Webb Space Telescope revealed so many early galaxies that we felt we needed to test its results with the best observatory on Earth,” said lead author Tom Bakx of Nagoya University in a statement. “It’s been a very exciting time being an observing astronomer and we’ve been able to follow the status of the observations that will test the JWST results in real time.”

The finding supports the fact that the galaxies observed by Webb include some of the oldest known galaxies, showing how powerful our tools now are for looking back at the early stages of the Universe.

“These deep ALMA observations provide robust evidence for the existence of galaxies in the first few hundred million years after the Big Bang and confirm the surprising results of the Webb observations,” said Jorge Zavala of the National Astronomical Observatory of Japan. “JWST’s work has only just begun, but we are already adapting our models of galaxy formation in the early Universe to these observations. The combined performance of Webb and the ALMA radio telescope array gives us the confidence to push our cosmic horizons ever closer to the dawn of the universe.”

The research results are published in the journal Monthly Notices of the Royal Astronomy Society.

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