Monday, September 24, 2007

Hidden Galaxies detected

Until now astronomers couldn't see foreground galaxies outshined by the dazzling quasars behind them. The difficulty in actually spotting and seeing these galaxies stems from the fact that the glare of the quasar is too strong compared to the dim light of the galaxy.

A new technique can pick apart the intense pattern of light emitted by quasars, finding irregularities in the image where "invisible" galaxies are absorbing some of the quasar light.

Quasars are small, distant and extremely bright cosmic beacons that produce more light than typically comes from an entire large galaxy. In spite of their brightness, however, some of the light is soaked up by intervening objects during its long journey to Earth's telescopes.

To locate the so-called "invisible" galaxies, Nicholas Bouche - an astronomer at the Max Planck Institute for Extraterrestrial Physics in Munich, Germany - and his team looked through huge catalogues of quasar data and picked out those with "dips" in their light signatures. Then, using the European Southern Observatory's (ESO) Very Large Telescope (VLT), located in the mountains of northern Chile, the team searched for galaxies close to the pulse of quasar light.

The astronomers capitalized on the VLT's special infrared spectrometer, called SINFONI, to pick apart 20 patches of sky around the quasars to search for galaxies from the time when the universe was about 6 billion years old. Seventy percent of the time, they found a galaxy hiding in the "headlights" of a quasar.

The astronomers who pioneered the technique have detected 14 hidden galaxies by targeting the VLT on unusual quasar light signatures. Bouche said he is surprised by not only the amount of galaxies he and his colleagues have found hiding near quasars, but also by the types of these galaxies. "These are not just ordinary galaxies," he said. "They are actively forming a lot of new stars and qualifying as starburst galaxies."

Source: Space dotcom
Quasar Jets Create Cosmic Pileups
Hidden Black Holes Found Behind Gas Veils at Quasars
Screaming to the Stars, Quasar Echos from Pamela Star Stryder

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