An oxygen galaxy recently imaged by astronomers using the ALMA observatory is home to the most distant deposits of that element ever seen in space. The observation was made in one of the oldest galaxies seen in the visible universe.
The ancient galaxy SXDF-NB1006-2 sits roughly 13.1 billion light years from Earth, and is seen as it was soon after light first began to traverse the darkness of space. The Big Bang took place roughly 13.8 billion years in the past, and light was first seen hundreds of millions of years later. Astronomers who found this distant oxygen galaxy were examining the chemical makeup of the ancient galaxy, hoping to learn more about the nature of these archaic bodies.
"Seeking heavy elements in the early Universe is an essential approach to explore the star formation activity in that period. Studying heavy elements also gives us a hint to understand how the galaxies were formed and what caused the cosmic reionization," Akio Inoue of Osaka Sangyo University in Japan said.
Prior to the formation of celestial objects, the universe was inundated with electrically-neutral gas. As the first light began to shine, electromagnetic radiation began to ionize this material, a process labeled as cosmic reionization.
The search for ionized oxygen in the distant family of stars involved examining other nearby galaxies to determine if ionized oxygen could even be seen at the great distances at which SXDF-NB1006-2 resides. Researchers determined the element could be measured, even from more than 13 billion light years away, and the substance was seen at a concentration around 10 percent that seen in the sun. Although that result was predicted, investigators were surprised to also find a small amount of dust in the system.
The detection of oxygen in the galaxy suggests that several stars, many times as larger than the sun, are bathing the galaxy in ultraviolet light, ionizing the gas.
Astronomers who participated in the study believe their investigation may shed light on the distant era during which we see SXDF-NB1006-2. All elements heavier than lithium were created by dying stars, so this finding suggests at least one generation of stars had already perished in the galaxy, even that early in the history of the universe.
When this ancient galaxy was first seen in 2012, it was the oldest galaxy known to astronomers. Since that time, researchers have found several galaxies older than that distant oxygen galaxy. When the object was first seen, a large cloud of ionized hydrogen was detected, encompassing the distant collection of stars.
Detection of oxygen in SXDF-NB1006-2 and analysis of the properties of the ancient galaxy was published in the journal Science.