Astronomers at NOIRLab have identified a groundbreaking pair of quasars using the powerful GNIRS instrument on the Gemini North telescope, part of the International Gemini Observatory operated by NSF NOIRLab. These quasars are confirmed to have formed during the earliest epochs of the Universe and represent the most distant merging quasar pair ever found. The findings have been published in the Astrophysical Journal Letters.
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The US National Science Foundation partially funds the research. The Universe has expanded since the first instant following the Big Bang. This implies that early-formed galaxies had a higher chance of interacting and merging and that the early Universe was significantly smaller. Quasars are incredibly bright galactic cores where gas and dust fall into a central supermassive black hole and emit enormous amounts of light, formed due to galaxy mergers.
Therefore, as their host galaxies merge, astronomers anticipate finding many pairs of quasars close to one another when looking back into the early Universe. They were shocked to discover that none had existed up until this point.
Astronomers have identified two merging quasars visible just 900 million years after the Big Bang using the Gemini North telescope, which is one-half of the International Gemini Observatory. The International Gemini Observatory is run by NSF NOIRLab and partially funded by the US National Science Foundation. This is the first pair of merging quasars confirmed during the Cosmic Dawn era of the Universe's history and the most distant pair ever discovered.
Between 50 million and one billion years passed after the Big Bang during the Cosmic Dawn. The first stars and galaxies emerged during this time, illuminating the previously dark universe. The Epoch of Reionization, which began with the arrival of the first stars and galaxies, marked the beginning of a new phase in the universe's formation.
Within Cosmic Dawn, there was a cosmological transition during the Epoch of Reionization. The universe's first stars, galaxies, and quasars emitted ultraviolet light about 400 million years after the Big Bang. This light interacted with the intergalactic medium and stripped the universe's primordial hydrogen atoms of their electrons, a process known as ionization. Large structures currently seen in the local universe were first observed during the crucial epoch of Reionization, which ended the cosmic dark ages.
Astronomers are interested in locating and analyzing quasars that populated this early and distant era to determine the precise role of quasars during the Epoch of Reionization.
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.
Yoshiki Matsuoka, Astronomer and Study Lead Author, Ehime University
About 300 quasars were found in the Epoch of Reionization; however, none of them were found in pairs. That is until Matsuoka and his colleagues noticed a slight red patch while examining photos obtained using the Hyper Suprime-Cam on the Subaru Telescope.
While screening images of quasar candidates I noticed two similarly and extremely red sources next to each other. The discovery was purely serendipitous.
Yoshiki Matsuoka, Astronomer and Study Lead Author, Ehime University
Since far-off quasar candidates are frequently contaminated by various sources, including foreground stars, galaxies, and the effects of gravitational lensing, the team was unsure that they were a quasar pair. To confirm the nature of these objects, the team used the Gemini Near-Infrared Spectrograph (GNIRS) on Gemini North and the Subaru Telescope's Faint Object Camera and Spectrograph (FOCAS) to perform follow-up spectroscopy.
The GNIRS spectra, which dissect a source's light emission into its wavelengths, were essential in determining the characteristics of the quasar pair and the galaxies that housed them.
What we learned from the GNIRS observations was that the quasars are too faint to detect in near-infrared, even with one of the largest telescopes on the ground.
Yoshiki Matsuoka, Astronomer and Study Lead Author, Ehime University
This enabled the team to estimate that some of the light observed in the optical wavelength range originates from ongoing star formation occurring in the host galaxies of the quasars rather than from the quasars themselves. The team also discovered that the two black holes are enormous, each with 100 million times the mass of the Sun. This implies that the two quasars and their host galaxies are undergoing a significant merger, as does the existence of a gas bridge between them.
Matsuoka said, “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.”
The Epoch of Reionization links the initial formation of cosmic structures to the intricate Universe observed billions of years later. Astronomers can learn a great deal about the formation of the first objects in the universe and the reionization process by examining far-off objects from this era. With the NSF-DOE Vera C. Rubin Observatory's ten-year Legacy Survey of Space and Time (LSST), starting in 2025, more discoveries like these could be in store. With its deep imaging capabilities, LSST is expected to detect millions of quasars.
Journal Reference:
Matsuoka, Y., et al. (2024) Discovery of Merging Twin Quasars at z = 6.05. The Astrophysical Journal Letters. doi.org/10.3847/2041-8213/ad35c7