Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected water and carbon monoxide molecules in a larger member of SPT-S J031132-5823.4 (SPT0311-58 for short), a pair of galaxies seen when the Universe was only 780 million years old. This detection suggests that the molecular Universe was going strong shortly after the elements were forged in early stars.
This artist’s conception shows the dust continuum and molecular lines of carbon monoxide and water seen in the pair of galaxies known as SPT0311-58. Image credit: ALMA / ESO / NAOJ / NRAO / S. Dagnello, NRAO.
First spotted by ALMA in 2017, SPT0311-58 is made up of two giant star-forming galaxies.
It is the most massive infrared luminous system discovered so far during the Epoch of Reionization, which occurred at a time when the Universe was just 780 million years old — roughly 5% of its current age — and the first stars and galaxies were being born.
Astronomers believe that the SPT0311-58 galaxies may be merging, and that their rapid star formation is not only using up their star-forming gas, but that it may eventually evolve the pair into massive elliptical galaxies like those seen in the Local Universe.
“Using high-resolution ALMA observations of molecular gas in the pair of galaxies known collectively as SPT0311-58 we detected both water and carbon monoxide molecules in the larger of the two galaxies,” said Sreevani Jarugula, a Ph.D. student at the University of Illinois.
“Oxygen and carbon, in particular, are first-generation elements, and in the molecular forms of carbon monoxide and water, they are critical to life as we know it.”
“This galaxy is the most massive galaxy currently known at high redshift, or the time when the Universe was still very young.”
“It has more gas and dust compared to other galaxies in the early Universe, which gives us plenty of potential opportunities to observe abundant molecules and to better understand how these life-creating elements impacted the development of the early Universe.”
These images show the molecular lines and dust continuum seen in ALMA observations of SPT0311-58. On left: a composite image combining the dust continuum with molecular lines for water and carbon monoxide. On right: the dust continuum seen in red (top), molecular line for water shown in blue (second from top), molecular line transitions for carbon monoxide, CO(6-5) shown in purple (middle), CO(7-6) shown in magenta (second from bottom), and CO(10-9) shown in pinks and deep blue (bottom). Image credit: ALMA / ESO / NAOJ / NRAO / S. Dagnello, NRAO.
Studying the first galaxies to form in the Universe helps astronomers to better understand the birth, growth, and evolution of the Universe, and everything in it, including the Solar System and Earth.
“Early galaxies are forming stars at a rate thousands of times that of the Milky Way,” Jarugula said.
“Studying the gas and dust content of these early galaxies informs us of their properties, such as how many stars are being formed, the rate at which gas is converted into stars, how galaxies interact with each other and with the interstellar medium, and more.”
“There’s plenty left to learn about SPT0311-58 and the galaxies of the early Universe,” she added.
“This study not only provides answers about where, and how far away, water can exist in the Universe, but also has given rise to a big question: How has so much gas and dust assembled to form stars and galaxies so early in the Universe?”
“The answer requires further study of these and similar star-forming galaxies to get a better understanding of the structural formation and evolution of the early Universe.”
“This exciting result, which shows the power of ALMA, adds to a growing collection of observations of the early Universe,” said Dr. Joe Pesce, an astrophysicist and ALMA program director at the National Science Foundation.
“These molecules, important to life on Earth, are forming as soon as they can, and their observation is giving us insight into the fundamental processes of a Universe very much different from today’s.”
The results will be published in the Astrophysical Journal.
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Sreevani Jarugula et al. 2021. Molecular Line Observations in Two Dusty Star-Forming Galaxies at z = 6.9. ApJ, in press; arXiv: 2108.11319
