Astronomers Discover The Earliest Galaxy Merger Yet

Artist’s impression of the merging galaxies, known as B14-65666. National Astronomical Observatory of Japan.

An international team of researchers has discovered the earliest example of a collision between two galaxies. The light from this merger had to travel for 13 billion years to reach us as it was produced just a few hundred million years after the Big Bang.

The system is known as B14-65666. Astronomers used the powerful ALMA (Atacama Large Millimeter/submillimeter Array) observatory to study it and detected oxygen, carbon, and dust. This is the earliest object for which signals for all three have been detected. The findings are reported in the Publications of the Astronomical Society of Japan

The signals bring us complementary information about the dynamics and structures of B14-65666. The system had been previously observed using the Hubble Space Telescope. Two blobs of stars were identified. The ALMA data showed that they are part of the same system but moving at different speeds, strongly suggesting we are seeing two galaxies clashing.

“With rich data from ALMA and HST, combined with advanced data analysis, we could put the pieces together to show that B14-65666 is a pair of merging galaxies in the earliest era of the universe,” lead author Dr Takuya Hashimoto, from the the Japan Society for the Promotion of Science and Waseda University, said in a statement. “Detection of radio waves from three components in such a distant object clearly demonstrates ALMA’s high capability to investigate the distant Universe.”

Composite image of B14-65666 showing the distributions of dust (red), oxygen (green), and carbon (blue), observed by ALMA and stars (white) observed by the Hubble Space Telescope. ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Hashimoto et al.

The team estimates that the two galaxies have about 10 percent of the stars found today in the Milky Way. But they are a lot more active, producing 100 times more stars per year than our galaxy does. This is another hallmark of an active merger taking place. As the two galaxies collide the gas is compressed and the system experiences bursts of star formation.  

Mergers are a key step in galaxy evolution. The Milky Way has experienced several in the past and will experience more in the future when Andromeda comes crashing towards it in a few billion years. To better understand what galaxies are like now, we need to study what they might have been like in the past. This is why an object like B14-65666 is so important.

“Our next step is to search for nitrogen, another major chemical element, and even the carbon monoxide molecule,” added co-author Professor Akio Inoue, also at Waseda University. “Ultimately, we hope to observationally understand the circulation and accumulation of elements and material in the context of galaxy formation and evolution.”


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