A team of astronomers has spotted the most distant merging galactic cores yet, seen as they were when the universe was less than a billion years old. The duo of active galactic centers, called quasars, is the only confirmed pair seen during the Cosmic Dawn.
The two very red galaxies were spotted by a team using the Subaru telescope’s Hyper Suprime-Cam at a redshift of z = 6.05 (indicating they are seen as they were over 12 billion years ago). To the average viewer, they look like nothing special: a couple faint red blotches in an image dazzling with closer galaxies and stars. But follow-up spectroscopic imaging of the objects helped the researchers determine that a quasar pair was the light source. The team’s research was published in The Astrophysical Journal Letters and a companion paper has been accepted for publication AAS Journals.
“A few hundreds of quasars are now known in the early universe, but none of them have been found in a pair,” Yoshiki Matsuoka, an astronomer at Japan’s Ehime University and the study’s lead author, told Gizmodo in an email. “This is contrary to a naive expectation from the standard theory of cosmology, which suggests that the universe has evolved via frequent mergers of galaxies, which would naturally result in many merging quasar pairs observed throughout the universe.”
“Our discovery provides the first evidence of such a pair actually present in the cosmic dawn,” Matsuoka added. “It supports the idea that the universe has evolved via mergers.”
The Cosmic Dawn is the period of time in the early universe when the first light sources formed. The period lasted from about 50 million years after the Big Bang to when the universe was one billion years old (it is now about 13.77 billion years old). Seeing quasars so early in the universe was long anticipated, so their direct observation is a welcome one.
At the heart of these quasars are black holes—regions of spacetime with gravitational fields so intense that light cannot escape them. That means that black holes are where all of astronomy’s perceptive instruments cease to have power, yielding the ground to astrophysical theories and simulations. The black holes in each quasar are each about 100 million times the mass of our Sun. Because the masses of the holes are about the same, Matsuoka said the team calls them twins.
“While it is only the first and single case, the present finding indicates that supermassive black holes and galaxies have indeed evolved through mergers with each other,” Matsuoka said. “It supports our standard paradigm of how the universe has evolved, under the strong pull of the gravity that affects every single bit of material.”
New eyes on the sky—such as the long-awaited Vera Rubin Observatory in Chile—will reveal more of the southern sky in real-time, helping astronomers classify objects near and far. The recent team is also proposing observations of the quasar pair with the Webb Space Telescope, to clarify the nature of gas flowing through the galaxies’ cores and how their gas might give way to stars.