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NASA's
Chandra Finds Evidence for Quasar Ignition
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An artist's
illustration depicts a quasar in the center of a galaxy that
has turned on and is expelling gas at high speeds in a
galactic superwind. Clouds of hot, X-ray producing gas
detected by Chandra around the quasars 4C37.43 (shown in the
inset) and 3C249.1, provide strong evidence for such
superwinds.
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New data from NASA's
Chandra X-ray Observatory may provide clues to how quasars "turn
on." Since the discovery of quasars over 40 years ago,
astronomers have been trying to understand the conditions
surrounding the birth of these immensely powerful objects.
Hot,
X-ray producing regions around two distant quasars observed by
Chandra are thought to have formed during their activation. These
features are located tens of thousands of light years from the
central supermassive black holes thought to power the
quasars.
"The X-ray features are likely shock waves
that could be a direct result of the turning on of the quasar
about 4 billion years ago," said Alan Stockton of the
University of Hawaii in Honolulu, and lead author of a report on
this work published recently in The Astrophysical Journal.
The
quasars, 4C37.43 and 3C249.1, showed no evidence for the
existence of a much larger envelope of hot gas around the
features, nor were the observed X-ray regions associated with
radio waves from the quasars. These factors rule out possible
explanations for the X-ray emitting clouds, such as the cooling
of hot intergalactic gas, or heating by high-energy jets from the
quasars.
"The best explanation for our observations
is that a burst of star formation, or the activation of the
quasar itself, is driving an enormous amount of gas away from the
quasar's host galaxy at extremely high speeds," said Hai Fu,
a coauthor of the study who is also from the University of
Hawaii.
Computer simulations of the formation of stars and
the growth of black holes during a collision between two galaxies
are consistent with this picture. The simulations, performed by
Tiziana Di Matteo of Carnegie-Mellon University in Pittsburgh,
Pennsylvania, and colleagues, show that the merger of galaxies
drives gas toward the central regions where it triggers a burst
of star formation and provides fuel for the growth of a central
black hole.
The inflow of gas into the black hole releases
a tremendous amount of energy, and a quasar is born. The power
output of the quasar dwarfs that of the surrounding galaxy and
expels gas from the galaxy in what has been termed a galactic
superwind. The Chandra data provide the best evidence yet for a
quasar-produced superwind.
Over a period of about 100
million years, the superwind will drive all the gas away from the
central regions of the galaxy, quenching both star formation and
further black hole growth. The quasar phase will end and the
galaxy will settle down to a relatively quiet life. The
tranquility of the galaxy will be interrupted from time to time
as a small satellite galaxy is captured and provides food for the
otherwise dormant supermassive black hole.
Other members of the research
team were J. Patrick Henry, also of the University of Hawaii, and
Gabriela Canalizo of the University of California, Riverside.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages
the Chandra program for the agency's Science Mission Directorate.
The Smithsonian Astrophysical Observatory provides science
support and controls flight operations from the Chandra X-ray
Center in Cambridge, Mass.
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Each
Image Contains A Hot Spot To Larger Graphic.
Information
on each image is below
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LEFT
IMAGE.
Chandra X-ray Image of
4C37.43
Clouds of hot, X-ray producing gas detected by Chandra
around the quasars 4C37.43 (shown above) and 3C249.1, provide
strong evidence for galactic superwinds, where a quasar in the
center of a galaxy has turned on and is expelling gas at high
speeds. The X-ray features seen at five, six, ten and eleven
o'clock (labeled c, a, d, b, respectively) in the 4C37.43 image
are located tens of thousands of light years from the central
supermassive black hole that powers the quasar. They are likely
due to shock waves in the superwind.
Scale: Image is 21
arcsec across
(Credit: NASA/CXC/Univ. of Hawaii/A.Stockton et
al.)
CENTER
IMAGE
Illustration of Galactic
Superwind
This artist's illustration depicts a quasar in the
center of a galaxy that has turned on and is expelling gas at
high speeds in a galactic superwind. Clouds of hot, X-ray
producing gas detected by Chandra around the quasars 4C37.43 and
3C249.1, provide strong evidence for such superwinds.
(Credit:
NASA/CXC/M.Weiss)
RIGHT
IMAGE
Hubble Optical Image of
4C37.43
This image from Hubble shows 4C37.43 - a quasar 4
billion light years from Earth - in visible light. The field of
view is slightly larger than the Chandra image shown above.
(Credit: NASA/STScI)
Source
/ Credit: NASA/CXC/M.Weiss; STScl /Univ. of Hawaii/A.Stockton et
al.
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