A double quasar has been discovered moving towards a major merger, lighting the ‘cosmic dawn’ just 900 million years after the Big Bang.
They are the first quasar few spotted so far back in cosmic time.
Quasars grow quickly supermassive black holes in the cores of hyperactive galaxies. Streams of gas are forced down the throats of the black holes and become trapped in the bottleneck of an accretion disk, a dense ring of ultra-hot gas lining up to fall into the black hole. It’s not all that bad; magnetic fields trapped in the rotating accretion disk are capable of whipping up a large number of charged particles and beaming them back into space in the form of two jets blasting off almost to the ground. speed of light. The combination of jets and accretion disk makes the quasar appear very luminous, even over billions light years.
Because every great galaxy has a monstrous galaxy black hole like its dark heat, when galaxies collide and merge, so does their supermassive black holes. During the cosmic dawn – which describes the first billion years of cosmic history, when stars and galaxies first appeared on the scene – expanding universe was smaller than now, and therefore galaxies were closer together and merged more often. But while more than 330 lone quasars have been observed in the first billion years of the universe so far, the expected abundant population of twin quasars is conspicuous by their absence – until now.
The newly discovered double quasar, J121503.42–014858.7 and J121503.55–014859.3 – named C1 and C2 by their discoverers – was spotted using the Subaru Telescope on Mauna Kea in Hawaii by a team led by Yoshiki Matsuoka of Ehime University in Japan.
The astronomers monitored this spectroscopically using the Faint Object Camera and Spectrograph (FOCAS) on Subaru and the Gemini Near-Infrared Spectrograph (GNIRS) on the Gemini North telescope, which also sits atop Mauna Kea.
“What we learned from the GNIRS observations is that the quasars are too faint to detect in the near-infrared, even with one of the largest ground-based telescopes,” Matsuoka said in a study. rack.
After traveling for 12.9 billion years, the light from the quasars has arrived redshifted and stretched to longer wavelengths by cosmic expansion, so that light that started out as X-rays or ultraviolet radiation ends up near the red and infrared ends of the Earth. electromagnetic spectrum. The light from the quasars should be observable in the near-infrared, but the fact that they are faint at that wavelength means that much of their light is actually at other wavelengths, produced by enhanced star formation in the galaxies in which the quasars occur.
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Increased star formation, estimated to be between 100 and 550 for C1 and C2 solar masses per year (compared to one to ten solar masses per year in our region). galaxy), is a common symptom of galaxy mergers, because the interaction sets raw molecular hydrogen gas into motion and encourages it to form new stars.
The two black holes are also within 40,000 light-years (12,000 parsecs) of each other. Although this is still a large distance, observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have found a gas bridge that spans this distance between C1 and C2. The two black holes are already connected, and that link will only grow stronger as they continue to approach each other.
The existence of C1 and C2 is further evidence that galaxies and their black holes exist grew fast, and to enormous size and mass, during the cosmic dawn era, challenging our models of how they should form. The black holes each have a mass of about 100 million times our mass Sunwhich is huge; Sagittarius A*, the black hole at the center of our Milky Way Galaxy, is small by comparison, with a mass of just 4.1 million solar masses. Furthermore, the host galaxies of C1 and C2 have a total mass of 90 billion and 50 billion solar masses respectively, which, while substantially less than the Milky Way, is still gigantic for that time.
As such, the discovery of this double quasar and their host galaxies provides an essential data point for better understanding the early Universe and especially the epoch of reionization, when most of the gas in the Universe was ionized by radiation from the first stars, galaxies and quasars, which put an end to the cosmic dark ages. One of the great puzzles of cosmology is which of these three things contributed most to the reionization.
“The statistical properties of quasars in the epoch of reionization tell us many things, such as the progress and origin of reionization, the formation of supermassive black holes during cosmic dawn, and the earliest evolution of the quasar hosts,” says Matsuoka.
We see these two quasars as they looked about 12.9 billion years ago. What has become of them since then? Simulations indicate that the two black holes will eventually merge in a burst gravitational waves. This will make the combined quasar even brighter and increase the star formation rate in the merged galaxy to above 1,000 solar masses per year, creating one of the most extreme galaxies in the universe. Ultimately, it could become one of the giants elliptical galaxies at the heart of a huge cluster of galaxies, such as M87 in the Virgo Cluster.
The findings were published on April 5 in The astrophysical diary lettersimmediately accompanying paper about the ALMA measurements.