Astronomers Discover Earliest Known Pair of Merging Quasars, Shedding Light on Cosmic Dawn

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This illustration depicts two quasars in the process of merging. Using both the Gemini North telescope, one half of the International Gemini Observatory, which is supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab, and the Subaru Telescope, a team of astronomers have discovered a pair of merging quasars seen only 900 million years after the Big Bang. Not only is this the most distant pair of merging quasars ever found, but also the first confirmed pair found in the period of the Universe known as Cosmic Dawn.

Astronomers have spotted two quasars – extremely bright cores of distant galaxies – locked in a cosmic dance just 900 million years after the Big Bang. This marks the first confirmed pair of quasars found so early in the Universe’s history, during a period known as the Cosmic Dawn.

The discovery, made using the Gemini North telescope in Hawaii, provides valuable insights into how the first stars and galaxies emerged, filling the dark Universe with light. It also sheds light on the Epoch of Reionization, when ultraviolet radiation from these early objects stripped electrons from hydrogen atoms that pervaded the cosmos.

Quasar Pairs Reveal Clues to Early Universe

Finding quasar pairs in the distant, early Universe can reveal important information, according to lead author Yoshiki Matsuoka of Ehime University in Japan. “The statistical properties of quasars in the Epoch of Reionization tell us many things, such as the progress and origin of the reionization, the formation of supermassive black holes during Cosmic Dawn, and the earliest evolution of the quasar host galaxies,” he said.

Over 300 individual quasars have been found from this epoch so far, but this marks the first confirmed pair. The two quasars were first noticed as faint red patches in images from the Subaru Telescope in Hawaii. Follow-up observations with Subaru and Gemini North confirmed their identity as a quasar duo.

Supermassive Black Holes Powering a Galactic Merger

Analysis showed that the two quasars are both powered by supermassive black holes 100 million times the mass of the Sun. A bridge of gas stretches between them, suggesting the two quasars and their host galaxies are in the process of merging together.

“The existence of merging quasars in the Epoch of Reionization has been anticipated for a long time. It has now been confirmed for the first time,” said Matsuoka. The finding matches expectations that quasar pairs should be more common in the early Universe, when galaxies interacted and merged more frequently.

Many more such discoveries may emerge in the coming years from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). Set to begin in 2025, LSST will scan the skies for a decade and is expected to uncover millions of quasars with its powerful imaging capabilities. This could greatly expand our understanding of how the first luminous objects emerged and evolved in the early Universe.

The research was published in the Astrophysical Journal Letters. Additional details on the quasar pair and their environment, based on observations from the Atacama Large Millimeter/submillimeter Array (ALMA), are presented in a companion paper.

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