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Evidence
for Ultra-Energetic Particles in Jet from Black Hole
For Release: June 20,
2006
New Haven, Conn. -- An international team of
astronomers led by researchers at Yale has obtained key infrared
observations that reveal the nature of quasar particle jets that
originate just outside super-massive black holes at the center of
galaxies and radiate across the spectrum from radio to X-ray
wavelengths; a complementary study of jet X-ray emission led by
astronomers at the University of Southampton, reaches the same
conclusion.
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Composite
of 3C273's jet, showing in which wavelength region the
emission peaks: X-rays (observed with Chandra) in blue,
optical light (observed with HST) in green, radio waves
(observed with the VLA) in red. Yellow indicates that both
optical and radio emission are strong.
Credit:
NASA/NRAO,
S.Jester, D.E.Harris, H.L.Marshall, K.Meisenheimer,
H.-J.Röser, & R.Perley
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Both studies involve the
jet of the quasar 3C273, famous since its identification in 1963
as the first quasar. It now appears that the most energetic
radiation from this jet arises through direct radiation from
extremely energetic particles, and not in the way expected by
most astronomers based on the previously available data. The two
reports, available now online in the Astrophysical Journal, will
appear in print in the September 10 issue.
"Quasar
jets, although extremely luminous, are so distant as to be
relatively faint and difficult to observe. Thanks to the
sensitivity of NASA's Great Observatories, we have been able to
map the 3C273 jet in infrared, visible light and X-rays,"
said C. Megan Urry, Israel Munson Professor of Physics and
Astronomy at Yale, and an author on one study. "These
combined data strongly suggest that ultra-energetic particles in
the 3C273 jet are producing their light via synchrotron
radiation."
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Composite showing
the relation between the quasar 3C273 (top left; the quasar
is a very small and bright source, the fuzz apparently
surrounding it is an artifact that appears when taking a
picture of a very bright source with a camera and telescope
for very faint things) and the jet. The color coding is the
same as in the image above.
Credit: NASA/NRAO, S.Jester,
D.E.Harris, H.L.Marshall, K.Meisenheimer, H.-J.Röser, &
R.Perley
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There have been two
competing theories of how emissions arise from the particles --
the "Inverse-Compton" theory proposing that the
emissions occur when jet particles scatter cosmic microwave
background photons, and the "Synchrotron Radiation"
theory postulating a separate population of extremely energetic
electrons or protons that cause the high-energy emission.
"The
Yale team used the Spitzer Space Telescope to observe 3C273
because it is located in space and is more sensitive to faint
infrared jet emission than any previous telescope," said
Yasunobu Uchiyama, a team leader and former postdoctoral fellow
at the Yale Center for Astronomy. Spitzer observations enabled
the team, with collaborators at Stanford, University of
Southampton, Goddard Space Flight Center, and the Brera
Observatory in Milan, to determine the infrared spectrum for the
first time and thus to realize its close connection to the X-ray
emission.
Sebastian Jester, now at the University of
Southampton, led a complementary study that used the Chandra
X-ray Observatory. This team, with collaborators at MIT Kavli
Institute for Astrophysics and Space Research and the Smithsonian
Astrophysical Observatory (SAO) in Cambridge, MA, and at the Max
Planck Institute for Astronomy in Heidelberg, obtained the first
detailed study of energy distribution of X-rays from the jet,
which also supported the synchrotron theory.
According to
the researchers, while the lifetime of the X-ray producing
particles is only about 100 years, the data indicate that the
visibly brightest part of the jet has a length of about 100,000
light years. Since there would be insufficient time for the
particles to shoot out from the black hole at close to the speed
of light and then release their energy as radiation as far out as
they are seen, the particles have to be accelerated locally,
where they produce their emission. Both teams also used data from
the third of NASA's Great Observatories, the Hubble Space
Telescope, and the radio telescopes of the Very Large Array
(VLA). The three space telescopes and the VLA "see"
emission of different wavelengths from celestial objects, and the
combined data was essential to reveal the new comprehensive
perspective on the jets. "The new observations show that the
flow structure of this jet is more complicated than had been
assumed previously," Jester explains. "That the present
evidence favors the synchrotron model deepens the mystery of how
jets produce the ultra-energetic particles that radiate at X-ray
wavelengths."
"Our results call for a radical
rethink of the physics of relativistic jets that black holes
drive," said Uchiyama. "But, we now have a crucial new
clue to solving one of the major mysteries in high-energy
astrophysics."
Basic
facts about 3C273
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Credit: SFL ORG.
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3C273 is a Quasar, the
astronomical term for the intense emission from extremely hot
matter that is about to disappear into a black hole. 3C273 is the
first object that was called a quasar.
Location Constellation Virgo,
RA 12:29:06.6997, DEC +02:03:08.598
Visual magnitude 13
Distance 755 Mpc = 2,500
million lightyears
Mass of black hole 886 million
solar masses (Peterson et al. 2004, ApJ 613, 682)
Other
authors on the papers include Jeffrey Van Duyne and Paolo Coppi
at Yale; C.C. Cheung at Stanford University; Rita Sambruna at
NASA/GSFC, Greenbelt, MD; Tadayuki Takahashi at ISAS/JAXA, Japan;
Laura Maraschi and Fabrizio Tavecchio at the Osservatorio
Astronomico di Brera, Milan; Dan Harris from the SAO; Herman
Marshall at MIT; and Klaus Meisenheimer at Max Planck Institute
for Astronomy in Heidelberg. Grant and contract funding from NASA
supported the research.
Source
/ credit: Yale University / Chandra X- Ray NASA/CXC/SAO / SFL
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