ATLANTA The universe is laden with massive galaxies that formed while the universe was just one billion years old, an era when such mature galaxies were not expected to exist.
Astronomers with the Gemini Deep Deep Survey have found an abundance of galaxies in the "redshift desert," a region of space thought to be sparse because of the time needed for massive galaxies to form. But a wealth of patience, combined with long telescope exposure times, has shed some new light on the matter.
"These massive galaxies seem to be forming surprisingly early," said Robert Abraham, an astronomer with the University of Toronto. Abraham is co-investigator of the Gemini team that conducted the study. "Its probably not at the point where we have to reevaluate our theories of galaxy formation, but its getting there."
The discovery was presented here today at a meeting of the American Astronomical Society.
Astronomers have generally believed that massive galaxies, such as elliptical galaxies, form when two spiral galaxies converge. That process, however, is slow, taking billions of years. Abraham and his colleagues found massive galaxies in full swing just 4.5 billion years after the big bang.
"Theyre already very old," explained Patrick McCarthy, a co-principal investigator on the study from the Observatories of the Carnegie Institution. "In fact, theyre ancient."
The galaxies appear to have formed when the universe was just one billion years old, too soon for galaxies pairs to collide and form much more massive galaxies.
Previous surveys had not found the massive galaxies because they are not forming stars as actively as other, smaller galaxies, and so do not shine so brightly.
Abraham, McCarthy and their colleagues used the Gemini North telescope at the Gemini Observatory in Hawaiis Mauna Kea. By keeping the telescopes aperture open for unprecedented stretches of time -- about 27 to 30 hours per exposure -- researchers were able to detect both old galaxies without a hint of star birth within them, as well as young galaxies teeming with stellar formation.
"Its certainly not a very fast method of observation," said Karl Glazebrook, who developed the technique, called nod and shuffle, for the eight-meter Gemini Telescope. He is also participated in the new study. "But it allows us to detect these galaxies that are 300 times fainter than the night sky."
The nod and shuffle technique constantly images a region then moves the telescope slightly, allowing researchers to isolate faint galaxies from the brighter night sky. The GDDS is nearly 80 percent complete, project researchers said, adding that they have confirmed some 120 redshifted galaxies within the "redshift desert." About two-thirds of the universe is made up of these old, red galaxies, they added.
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