Deer can't
see cars at night because of blindingly bright headlights. And until now,
astronomers couldn't see foreground galaxies outshined by the dazzling quasars
behind them.
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.
"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," said Nicholas Bouche, an astronomer at the Max Planck Institute
for Extraterrestrial Physics in Munich, Germany.
Bouche and
his team's findings will be detailed in an upcoming issue of Astrophysical
Journal.
Very
large help
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, Bouche 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, almost
half its current age. Seventy percent of the time, they found a galaxy hiding
in the "headlights"
of a quasar.
So far, the
astronomers who pioneered the technique have detected 14 hidden galaxies by
targeting the VLT on unusual quasar light signatures.
Galaxy
hunt
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.'"
These types
of galaxies are forming the equivalent of about "20 suns per year,"
noted team member Celine Peroux, an astronomer at the Institute of Astronomy in Cambridge.
The team
thinks their finding will spur a new hunt for galaxies in the universe.
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