-The discovery, published Wednesday in the journal Nature, could force cosmologists to change their models of the universe. Most models don't predict such an abundance of massive galaxies so early in the evolution of the universe.
"This is the first time that such a large population of massive galaxies was confirmed during the first 2 billion years of the 13.7-billion-year life of the universe. These were previously invisible to us," Tao Wang, researcher at the University of Tokyo, said in a news release. "This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now."
The newly discovered galaxies are invisible to the naked eye. Not even the Hubble Space Telescope can detect them -- their light is too faint, the wavelengths too long.
With Hubble unable to help, astronomers had to look elsewhere.
"We turned to the Atacama Large Millimeter/submillimeter Array, ALMA, which is ideal for viewing these kinds of things," said Kotaro Kohno, a professor of astronomy. "I have a long history with that facility and so knew it would deliver good results."
Because the universe is expanding, light gets stretched as it travels long distances through space. This makes especially large galaxies from the early universe hard to spot. However, the phenomenon allows astronomers to calculate how far away the light traveled from, making it possible for astronomers to date the origins of these elusive, ancient galaxies.
"It was tough to convince our peers these galaxies were as old as we suspected them to be. Our initial suspicions about their existence came from the Spitzer Space Telescope's infrared data," said Wang. "But ALMA has sharp eyes and revealed details at submillimeter wavelengths, the best wavelength to peer through dust present in the early universe. Even so, it took further data from the imaginatively named Very Large Telescope in Chile to really prove we were seeing ancient massive galaxies where none had been seen before."
The discovery has implications for scientists' understanding of the evolution of supermassive black holes in the early universe. The bigger the galaxy, the bigger the supermassive black hole at its center.
"Massive galaxies are also intimately connected with the distribution of invisible dark matter," Kohno said. "This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now."