Initially identified by the JWST GLASS Survey, GHZ2/GLASS-12 existed at a time when the Universe was just 367 million years old. (redshift Z=12.117).
This is a distant galaxies GHZ2/GLASS-1212. Image credit: NASA / ESA / CSA / T. Treu, UCLA / NAOJ / T. Bakx, Nagoya University.
The JWST GLASS Survey identified GHZ2/GLASS-12, which is a study of the distant Universe that studies massive galaxies and their clusters.
This collection of observations consists of multiple images that are processed with different wide-band colors, much like the RGB color filter on a camera.
The light from distant galaxies takes so long to reach us, that it is difficult for the universe’s expansion to shift the color towards the red spectrum. This phenomenon is called the redshift.
Astronomers were able to identify GHZ2/GLASS-1212 by its red color.
In the initial few weeks of Webb observation, so many distant and bright galaxies were found that we had to question our understanding of how they formed.
These red hues are not indicative of distant galaxies, but could be an extremely dusty galaxy disguised as one.
The true distances between these galaxies can only be confirmed by direct observation of the spectral line — which is a spectrum that an element uses to identify it — in the galaxy’s visible light spectrum.
Immediately after the discovery of these early galaxy candidates, Dr. Tom Bakx from Nagoya University and the National Astronomical Observatory of Japan and colleagues used the Atacama Large Millimeter/submillimeter Array (ALMA) to hunt for a spectral line to confirm the true ages of the galaxies.
ALMA was pointed at Ghaz2/GLASS-12 to search for an emission line that is associated with oxygen at the frequency predicted by Webb’s observations.
Because oxygen is an element that is abundant in galaxies far away due to its short timescale of formation, the authors searched for an oxygen emission line. This increased detection rate would increase.
ALMA detected the emission line near the location of the galaxies.
We see the galaxy in its original 367 million year-old state (z=12.117), based on the observed redshift.
Dr. Bakx stated that Webb’s first images revealed many galaxies early in the universe, and that he felt it was necessary to verify its findings using an Earth-based observatory.
It was an exciting time to work as an observatory astronomer. We could monitor the progress of observations that would test the Webb results live.
We were initially worried about the small variation between the oxygen emission line detected and Webb’s galaxy. However, we did detailed testing on observations and confirmed that it really was a strong detection. It is extremely difficult to explain any other explanation.
According to Dr. Jorge Zavala of the National Astronomical Observatory of Japan, “The bright-line emission suggests that this galaxy quickly enriched their gas reservoirs with elements lighter than hydrogen or helium.”
This gives us clues as to the origin and evolution of first stars, and the duration of their lives.
The small separation between stars’ emission and oxygen gas might indicate that the early galaxies were subject to violent explosions, which blew gas from their galaxy center into the area surrounding it and beyond.
These deep ALMA observations confirm the unexpected Webb results and provide strong evidence for the existence galaxies in the very first 100 million years following the Big Bang.
Webb’s work is just beginning, and we have already adjusted our models for how galaxies formed in the early Universe to correspond with these observations.
Webb’s combined power and ALMA radio telescope array give us confidence in our ability to see the dawn of the Universe from the horizons of space.
These findings were published by the Monthly Notices of The Royal Astronomical Society.
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Tom J.L.C. Bakx The authors and others. Deep ALMA redshift searching of a candidate galaxy for z 12 GLASS–JWST MNRAS, published online December 23, 2022; doi: 10.1093/mnras/stac3723