Using a gamut of telescopes, astronomers have spotted the brightest galaxies in the distant, young universe. The galaxies are located about 12 billion light-years away, and are the most luminous and massive galaxies seen at that great distance.
Washington, Aug 10 : Using a gamut of telescopes, astronomers have spotted the brightest galaxies in the distant, young universe. The galaxies are located about 12 billion light-years away, and are the most luminous and massive galaxies seen at that great distance.
The scientists said the newfound galaxies are intrinsically bright due to their large rate of star formation -1000 times greater than the Milky Way. However, surrounding dust and gas, leaking out only in the infrared, has hidden much of that light, they said.
These are also among the oldest galaxies in the universe and existed when it was less than two billion years old, they said.
Lead author of the study Giovanni Fazio, a Harvard-Smithsonian Center for Astrophysics (CfA) astronomer said, smaller, dimmer galaxies were much more common in the early universe because it took time for galaxies to form and grow.
"It's a real surprise to find galaxies that massive and luminous existing so early in the universe. We are witnessing the moment when the most massive galaxies in the universe were forming most of their stars in their early youth," he said.
"It's tough to explain how such bright, massive, dusty galaxies formed so early in the lifetime of the universe," added Harvard graduate student Josh Younger.
The astronomers initially spotted the hide-and-seek galaxies with the AzTEC imaging camera on the James Clerk Maxwell Telescope.
The camera, developed by a team led by Grant Wilson and Min Yun of the University of Massachusetts at Amherst, discovered several hundred previously unseen galaxies that were bright at the millimetre and sub-millimetre wavelengths.
A team of astronomers made follow-up observations of the seven brightest galaxies in an area of the sky studied by the Cosmic Evolution Survey (COSMOS). The Smithsonian's Sub-millimetre Array pinpointed the exact location of each galaxy, allowing the team to confirm that the source was a single galaxy and not a blend of several fainter galaxies.
Once precise locations were known, additional observations were made with the Hubble, the Spitzer Space Telescope, and the Very Large Array of radio telescopes in Chile.
While Hubble could not detect the galaxies, confirming that they are shrouded in dust that blocks visible light; Spitzer could penetrate the dust and detect the stars directly. The Very Large Array detected only the two closest galaxies.
By combining these measurements, the astronomers showed that five of the seven AzTEC galaxies are located at redshifts greater than 3, which corresponds to a distance of 12 billion light-years.
"These results suggest that the brightest submillimeter galaxies may be the most distant," said Fazio, adding that the galaxies' large infrared brightness indicated that they were forming new stars rapidly, probably due to collisions and mergers.
"The source of the infrared radiation seems to be very compact, which suggests that they are colliding galaxies that may eventually evolve into quasars," added Younger.
Younger said the team's future plan was to image more sources of sub-millimetre radiation in different cosmic environments, to try to better understand the population.
"We also plan to use the most extended configuration of the SMA to zoom in and try to resolve these objects, and really narrow down the source of their extreme infrared luminosity," said Younger.
The results of the study are scheduled for publication in the Astrophysical Journal.
ANI