Astronomers calculate the age of the most distant galaxy with oxygen

25 Jan. () –

A study by a joint team from Nagoya University and the National Astronomical Observatory of Japan has measured the cosmic age of a galaxy far, far away: 367 million years after the Big Bang.

The team used the ALMA radio telescope array to detect a radio signal that has been traveling for about 97% of the age of the Universe. This discovery confirms the existence of galaxies in the very early Universe discovered by the James Webb Space Telescope (JWST). The research is published in Monthly Notices of the Royal Astronomical Society.

The galaxy, named GHZ2/GLASS-z12, was initially identified in the JWST GLASS survey, a survey that looks into the distant Universe and behind massive clusters of galaxies. These observations consist of multiple images using different broadband color filters, similar to separating RGB colors in a camera.

In the case of distant galaxies, light takes so long to reach us that the expansion of the Universe has shifted the color of this light towards the red end of the visible light spectrum in the so-called redshift. Consequently, the red color of GHZ2/GLASS-z12 helped the researchers to identify it. as one of the most convincing distant galaxy candidates they had observed.

OXYGEN ASSOCIATED EMISSION LINE

In the first few weeks of JWST observations, so many bright distant galaxies were identified that they called into question our basic understanding of the formation of the first galaxies. However, these red colors are only indicative of a distant galaxy, and could rather be a very dusty galaxy masquerading as a more distant object. Only direct observations of spectral lines – lines present in the light spectrum of a galaxy that are used to identify the elements present – can strongly confirm the true distances of these galaxies.

Immediately after the discovery of these first candidate galaxies, two first-time researchers from Nagoya University and the National Astronomical Observatory of Japan used the forty radio telescopes of the ALMA array in Chile. to search for a spectral line that would confirm the true age of the galaxies.

ALMA targeted GHZ2/GLASS-z12 to search for an oxygen-associated emission line at the expected frequency suggested by the JWST observations. Oxygen is a typically abundant element in distant galaxies due to its relatively short time scale of formation, so the team opted to search for an oxygen emission line to increase the chances of detection.

367 MILLION YEARS AFTER THE BIG BANG

By combining the signal from each of its 12-meter telescopes, ALMA was able to detect the emission line close to the galaxy’s position. The observed redshift of the line indicates that we see the galaxy as it was just 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 had to test their results using the best observatory on Earth,” he says. it’s a statement lead author Tom Bakx of Nagoya University. “It was a very exciting time to be an observational astronomer, and we were able to follow the status of the observations that will test the JWST results in real time.”

“We were initially concerned about the slight variation in position between the detected oxygen emission line and the galaxy seen by Webb,” says lead author Tom Bakx, “but we did detailed testing of the observations to confirm that this is indeed a robust detection. , and it is very difficult to explain by any other interpretation.”