ALMA finds the first example of galaxy fusion

Researchers using ALMA (Atacama Large Millimeter / Submillimeter Array) have observed oxygen, carbon and dust signals from a galaxy at the beginning of the Universe 13 billion years ago. ; years. This is the first galaxy where this useful combination of three signals has been detected. By comparing the different signals, the team determined that the galaxy was actually a fusion of two galaxies, making it the first example of galaxy fusion ever discovered.

Takuya Hashimoto, a postdoctoral researcher at the Japan Society for the Promotion of Science and Waseda University, and his team used ALMA to observe the B14-65666, an object located 13 billion light years away from the constellation of Sextans. Because of the speed of light, the signals we receive from B14-65666 have had to travel for 13 billion years to reach us. In other words, they show us the picture of what the galaxy looked like 13 billion years ago, less than a billion years after the Big Bang .

ALMA detected radio emissions of oxygen, carbon and dust in B14-65666. It is the oldest galaxy where these three signals were detected. The detection of several signals is important because they contain additional information.

The data analysis showed that the emissions are divided into two blobs. Earlier observations with the Hubble Space Telescope (HST) had revealed two star clusters on B14-65666. Now, with the three transmit signals detected by ALMA, the team was able to show that the two blobs actually form a single system, but they have different speeds. This indicates that the blobs are two galaxies being merged. It is the oldest known example of galaxy fusion. The research team estimated that the total star mass of B14-65666 is less than 10% of that of the Milky Way. This means that B14-65666 is in the early stages of its evolution. Despite its youth, the B14-65666 produces stars 100 times more active than the Milky Way. Such active star formation is another important signature of galactic fusions, as the compression of gases in colliding galaxies naturally results in stellar splinter formation.

"With the rich data of ALMA and HST, combined with advanced data analysis, we could gather the elements to show that B14-65666 is a pair of fused galaxies at the very beginning of the universe," Hashimoto explains. "The detection of three component radio waves in such a distant object clearly demonstrates ALMA's great ability to explore the distant universe."

Modern galaxies like our milky way have known countless mergers, often violent ones. Sometimes a larger galaxy swallowed a smaller one. In rare cases, galaxies of similar sizes have merged to form a new, larger galaxy. Mergers are essential to the evolution of the galaxy, so many astronomers are eager to trace their history.

"Our next step is to look for nitrogen, another major chemical element, and even the carbon monoxide molecule," said Akio Inoue, a professor at Waseda University. "Ultimately, we hope to understand observably the circulation and accumulation of elements and materials in the context of the formation and evolution of galaxies."

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