"We pointed the more than forty 12-m antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) and the 6.5-m James Webb Space Telescope (JWST) for several hours at a sky position that would appear totally empty to the naked human eye, aiming to catch a signal from one of the most distant astronomical objects known to date," said Jorge Zavala, an astronomer at the East Asian ALMA Regional Center at the National Astronomical Observatory of Japan. "And successfully detected the emission from excited atoms of different elements such as Hydrogen and Oxygen from an epoch never reached before," he added. This marks the first time emissions of this kind have been detected in galaxies located more than 13 billion light-years away.

The study's origins trace back to JWST's initial extragalactic observations in 2022. Among the findings was the galaxy GHZ2 (also called GLASS-z12), one of the brightest and most distant galaxy candidates identified. Researchers emphasize that confirming and analyzing the properties of such objects is critical for testing theories on galaxy formation and evolution, as well as understanding the early stages of cosmic history. This requires detailed spectroscopic observations to identify specific atomic or molecular features. However, obtaining such data for these distant galaxies has been a significant challenge due to their extreme remoteness.

Recent observations have provided groundbreaking insights into the nature of these ancient galaxies. ALMA detected the [OIII] 88um transition from doubly ionized oxygen in GHZ2, placing it at a redshift of z=12.333. This corresponds to an era roughly 400 million years after the Big Bang when the universe was only 3% of its current age. The light from this galaxy has traveled an astonishing 13.4 billion years, making it the most distant object with multiple line detections across the electromagnetic spectrum and the first observed by ALMA at z>10. Combining these data with JWST observations from its NIRSpec and MIRI instruments allowed for a detailed characterization of the galaxy.

The findings reveal that GHZ2 is undergoing extreme bursts of star formation under unique conditions. The metallicity - the abundance of elements heavier than hydrogen - is significantly lower than in most previously studied galaxies. This is expected given the universe's youth at the time, yet the metallicity has reached about one-tenth of the solar level. The galaxy also hosts a young stellar population, with short-lived, massive, and hot stars contributing to its exceptional brightness, features not commonly seen in more evolved galaxies.

The total mass of GHZ2, a few hundred million times that of the Sun, is concentrated in a remarkably small region of under 100 parsecs. This indicates a stellar density comparable to that found in globular clusters - dense groups of old stars observed in the Milky Way and other galaxies. The study highlights striking similarities between GHZ2 and globular clusters, including low metallicity, chemical abundance anomalies, and intense star formation activity. Such objects may help explain the origins of globular clusters, a longstanding mystery in astrophysics.

"This study is a crown on the multi-year endeavour to understand galaxies in the early Universe," said Tom Bakx, a researcher at Chalmers University in Sweden and a former researcher at Nagoya University. He added that these observations set the stage for further investigations into the earliest phases of galaxy formation. "The analysis of multiple emission lines enabled several key tests of galaxy properties, and demonstrates the excellent capabilities of ALMA through an exciting, powerful synergy with other telescopes like the JWST," Bakx concluded.

Research Report:ALMA detection of [OIII] 88um at z=12.33: Exploring the Nature and Evolution of GHZ2 as a Massive Compact Stellar System

Research Report:A luminous and young galaxy at z = 12.33 revealed by a JWST/MIRI detection of Ha and [O III]

Research Report:JWST NIRSpec Spectroscopy of the Remarkable Bright Galaxy GHZ2/GLASS-z12 at Redshift 12.34

Research Report:Evidence of Extreme Ionization Conditions and Low Metallicity in GHZ2/GLASS-Z12 from a Combined Analysis of NIRSpec and MIRI Observations

Related Links
Atacama Large Millimeter/submillimeter Array (ALMA)
Understanding Time and Space