Image: Three galaxies
Scientists are trying to understand how galaxies formed when the universe was half its current age (upper panels). The same galaxies were then studied with the Very Large Telescope. Parts which are red are moving away from us, while those that are blue are moving towards us.
updated 3/17/2009 8:08:11 PM ET 2009-03-18T00:08:11

Distant galaxies once represented mere specks of light in the sky. But astronomers are now using Hubble and Europe's Very Large Telescope to obtain detailed 3-D views of galaxies dating back as far as six billion years.

The Hubble Space Telescope can scope out the structure of faraway galaxies, while the European Southern Observatory's VLT can use a spectrograph to reveal the motions of galactic gases. The combined 3-D view of ancient galaxies halfway across the known universe allows astronomers to trace mass and orbits relatively accurately.

"This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones," said Francois Hammer, an astronomer with the Paris Observatory in Meudon, France.

An international team has targeted about one hundred remote galaxies for 3-D reconstruction, starting with results for three galaxies viewed by both Hubble and VLT's spectrograph, also known as FLAMES/GIRAFFE.

One galaxy presented a mystery when FLAMES/GIRAFFE spotted its region of ionized gas, composed of atoms that have been stripped of one or more electrons. However, Hubble failed to detect any stars after 11 days of peering at the region.

"Clearly this unusual galaxy has some hidden secrets," said Mathieu Puech, another astronomer at the Paris Observatory. Computer simulations suggest that the super-heated region resulted from a collision between two gas-rich spiral galaxies, making it too hot for stars to form.

A second galaxy has become enshrouded in dust, with a reddish disc surrounding a bluish central region. That could mark the first example of a disk rebuilt after a major galactic merger.

"The models indicate that gas and stars could be spiraling inwards rapidly," Hammer noted.

The third galaxy contained a very blue, elongated structure made up of young, huge stars. Such a result could have arisen from an unequal collision between galaxies of different masses, according to simulations.

"The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over the past six to eight billion years, that is, over half the age of the Universe," Hammer said.

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