Astronomers at NOIRLab have identified an unprecedented pair of quasars using the powerful GNIRS instrument on the Gemini North telescope, part of the international Gemini Observatory operated by the NSF NOIRLab. These quasars are confirmed to have formed during the early epochs of the universe and represent the most distant merging quasar pair ever detected. The findings have been published in Astrophysical Journal Letters,
Image source: Mopic/Shutterstock.com
The U.S. National Science Foundation partially funds this research. The universe has been expanding since the first moment after the Big Bang. This means that initially formed galaxies were more likely to interact and merge and the early universe was much smaller. Quasars are incredibly bright galaxy centers where gas and dust fall into a central supermassive black hole and emit vast amounts of light, created by galaxy mergers.
So, astronomers expect to find many pairs of quasars close to each other when looking back into the early universe as their host galaxies merge together. They were surprised to find that none existed until this point.
Astronomers have identified two merging quasars that appeared just 900 million years after the Big Bang using the Gemini North telescope, half of the International Gemini Observatory. The International Gemini Observatory is operated by the NSF NOIRLab and partly funded by the U.S. 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.
During the cosmic dawn, 50 million to a billion years passed after the Big Bang. During this time the first stars and galaxies emerged, illuminating the previously dark universe. The era of reionization, which began with the arrival of the first stars and galaxies, marks the beginning of a new phase in the formation of the universe.
Within the cosmic dawn, a cosmic transformation occurred 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 original hydrogen atoms of their electrons, a process known as ionization. The large structures currently observed in the local universe were first observed during the critical epoch of reionization, which ended the cosmic dark ages.
Astronomers are interested in detecting and analyzing quasars that existed at this early and distant era, in order to determine the exact role of quasars during the reionization epoch.
The statistical properties of quasars in the reionization era tell us many things, such as the progression and origin of reionization, the formation of supermassive black holes during cosmic dawn, and the early evolution of quasar host galaxies,
Yoshiki Matsuoka, astronomer and lead author of the study, Ehime University
About 300 quasars were discovered in the reionization era; however, none of them were found in pairs. That was until Matsuoka and his colleagues noticed a faint red spot while examining images obtained using the Hyper Suprime-Cam on the Subaru Telescope.
While screening images of quasar candidates I noticed two similar and extremely red sources next to each other. This discovery was made entirely by chance,
Yoshiki Matsuoka, astronomer and lead author of the study, Ehime University
Because distant quasar candidates are often contaminated by a variety of sources, including foreground stars, galaxies, and the effects of gravitational lensing, the team was not sure they were a quasar pair. To confirm the nature of these objects, the team performed follow-up spectroscopy using the Gemini Near-Infrared Spectrograph (GNIRS) on Gemini North and the Subaru Telescope's Faint Object Camera and Spectrograph (FOCAS).
GNIRS spectra, which divide a source's light emission into its wavelengths, were essential in determining the properties of quasar pairs and the galaxies that house them.
From GNIRS observations we learned that quasars are so dim that they cannot be seen in the near-infrared, even with some of the largest telescopes on Earth.,
Yoshiki Matsuoka, astronomer and lead author of the study, Ehime University
This led the team to infer that some of the light observed in the optical wavelength range originates from ongoing star formation in the quasars' host galaxies, rather than the quasars themselves. The team also discovered that both black holes are extremely massive, with each having a mass more than 100 million times that of the Sun. This means that both quasars and their host galaxies are undergoing a significant merger, as evidenced by the existence of a gas bridge between them.
Matsuoka said,The existence of merging quasars in the era of reionization has been speculated for a long time. Now it has been confirmed for the first time,
The era of reionization connects the early formation of cosmic structures to the complex universe seen billions of years later. Astronomers can learn a lot about the formation of the first objects in the universe and the reionization process by examining distant objects from this era. With the NSF-DOE Vera C. Rubin Observatory's ten-year Legacy Survey of Space and Time (LSST), scheduled to begin in 2025, more discoveries like this may be made. With its deep imaging capabilities, the LSST is expected to detect millions of quasars.
Journal Reference:
Matsuoka, Y., and others(2024) Discovery of merging twin quasars at z = 6.05. Astrophysical Journal Letters. doi.org/10.3847/2041-8213/ad35c7
Source:
https://noirlab.edu/public/