Most Distant X-Ray Jet Yet Discovered Provides Clues To Big
Bang
The most distant jet
ever observed was discovered in an image of a quasar made by NASA's
Chandra X-ray Observatory. Extending more than 100,000 light-years
from the supermassive black hole powering the quasar, the jet of
high-energy particles provides astronomers with information about
the intensity of the cosmic microwave background radiation 12
billion years ago.
The discovery of this jet was a surprise to the astronomers,
according to team members. Astronomers had previously known the
distant quasar GB1508+5714 to be a powerful X-ray source, but there
had been no GB1508+ indication in previous images of any complex
structure or a jet.
"This jet is especially significant because it allows us to
probe the cosmic background radiation 1.4 billion years after the
big bang," said Aneta Siemiginowska of the Harvard-Smithsonian
Center for Astrophysics in Cambridge, Mass., lead author of a
report on this research in the November 20 Astrophysical Journal
Letters. Prior to this discovery, the most distant confirmed X-ray
jet corresponded to a time about 3 billion years after the big
bang.
Quasars are thought to be galaxies that harbor an active central
supermassive black hole fueled by infalling gas and stars. This
accretion process is often observed to be accompanied by the
generation of powerful high-energy jets. As the electrons in the
jet fly away from the quasar at near the speed of light, they move
through the sea of cosmic background radiation left over from the
hot early phase of the universe.
When a fast-moving electron collides with one of these
background photons, it can boost the photon's energy up into the
X-ray band. The X-ray brightness of the jet depends on the power in
the electron beam and the intensity of the background radiation.
"Everyone assumes that the background radiation will change in a
predictable way with time, but it is important to have this check
on the predictions,"
said Siemiginowska. "This jet is hopefully just the first in a
large sample of these distant objects that can be used to tell us
how the intensity of the cosmic microwave background changed over
time."
"In fact, if this interpretation is correct, then discovery of
this jet is consistent with our previous prediction that X-ray jets
can be detected at arbitrarily large distances!" said team member
Dan Schwartz, also of the Harvard-Smithsonian Center for
Astrophysics.
Chandra originally
observed GB 1508+5714 with the purpose of studying the X-ray
emission from the dust located between the Earth and the far-flung
quasar. The jet was found by Siemiginowska and her colleagues when
they examined the data once it became available publicly in the
Chandra archive. This led another astronomer to then carefully look
at radio observations of the object. Indeed, archived Very Large
Array data confirmed the existence of the jet associated with the
quasar GB 1508+5714. A paper on the radio observations of GB
1509+5714 has been accepted by Astrophysical Journal Letters from
Teddy Cheung of Brandeis University in Waltham, Mass.
Another group of astronomers led by Weimin Yuan of the
University of Cambridge, United Kingdom, independently reported the
discovery of the extended emission in GB 1508+5714 in X-rays. In a
paper to be published in an upcoming issue of the Monthly Notices
of the Royal Astronomical Society, the authors note that
significant energy is being deposited in the outer regions of the
host galaxy at a very early stage. This energy input could have a
profound effect on the evolution of the galaxy by triggering the
formation of stars, or inhibiting the growth of the galaxy through
accretion of matter from intergalactic space.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages
the Chandra program for the Office of Space Science, NASA
Headquarters, Washington.