Galaxies older than thought, team says

By Timothy Hurley
Advertiser Staff Writer

A team of scientists using the Gemini North Telescope atop Mauna Kea has thrown a popular theory of galactic evolution for a loop with new research showing that most galaxies were formed much earlier than thought.

The discovery by a multinational investigation called the Gemini Deep Deep Survey was announced today at the 203rd meeting of the American Astronomical Society in Atlanta.

Jean-Rene Roy, associate director of the Gemini North Telescope, said the research will cause scientists to rethink what happened 8 billion to 11 billion years ago.

"This changes the physics of galaxy formation theory," Roy said.

The current theory suggests that the population of galaxies in this early stage should have been dominated by evolutionary building blocks, that normal to large galaxies, like those studied in this project, would not yet exist and would instead be forming from local beehives of activity where big galaxies grew.

But that's not what the project found. Working over a 12-month period, the Gemini scientists used a sophisticated technique to capture the faintest galactic light ever dissected into the rainbow of colors called a spectrum. In all, spectra from more than 300 galaxies were collected, most from a relatively unexplored period when the universe was only 3 billion to 6 billion years old.

Such surveys in the past focused on galaxies where intense star formation was occurring, which makes it easier to obtain spectra but produces a biased sample, Roy said.

The team, which used more than 120 hours of telescope time, was able to look at a more representative sample, including dimmer and more massive galaxies that demanded a special technique to coax spectra from their dim light.

Roy said some now believe that black holes may have played a bigger role in the formation of the galaxies.

"The theoreticians will definitely have something to gnaw on," said Roberto Abraham, a lead investigator with the Gemini team.

The data will be released in four papers nearing completion for publication in The Astrophysical Journal and The Astronomical Journal.

Reach Timothy Hurley at thurley@honoluluadvertiser.com or (808) 244-4880.