Distant galaxies once represented mere specks of light in
the sky. But astronomers are now using Hubble and Europe's Very Large Telescope
(VLT) 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.
advertisement
