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RE: Quasar 3C273
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Title: The high-energy spectrum of 3C 273
Authors: Valentino Esposito, Roland Walter, Pierre Jean, Andrea Tramacere

The high energy spectral shape of 3C 273 is usually understood in terms of Inverse-Compton emission in a relativistic leptonic jet. This model predicts variability patterns and delays which could be tested if simultaneous observations are available from the infrared to the GeV range. The instruments IBIS, SPI, JEM-X on board INTEGRAL, PCA on board RXTE and LAT on board Fermi have enough sensitivity to follow the spectral variability from the keV to the GeV and to compare them with model predictions. We are presenting preliminary results on the high energy spectrum of 3C 273 and its variability and compare these results to predictions. We found that a single component is not able to adequately fit the multiwavelength spectrum (5 keV - 10 GeV) when the statistics in Fermi data is sufficient to constraint gamma-ray emission. This suggests that the X-rays emission is not originated in the jet. A possible explanation could be that X-rays are dominated by a Seyfert-like thermal inverse Compton.

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A lunar occultation of 3C 273 on the 5th August, 1962, enabled Australian radio astronomers to precisely fix the location of the previously known radio source 3C 273, in Virgo.

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3C 273 is a quasar located in the constellation Virgo. It was the first quasar ever to be identified.
The name signifies that it was the 273rd object (ordered by right ascension) of the Third Cambridge Catalogue of Radio Sources (3C), published in 1959. After accurate positions were obtained using lunar occultation on August 5, 1962, by Cyril Hazard at the Parkes Radio Telescope, the radio source was quickly associated with an optical counterpart, an unresolved stellar object.

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Title: Time Variation of Rotation Measure Gradient in 3C 273 Jet
Authors: Keiichi Asada, Makoto Inoue, Seiji Kameno, Hiroshi Nagai

The existence of a gradient in the Faraday rotation measure (RM) of the quasar 3C 273 jet is confirmed by follow-up observations. A gradient transverse to the jet axis is seen for more than 20 mas in projected distance. Taking account of the viewing angle, we estimate it to be more than 100 pc. Comparing to the distribution of the RM in 1995, we detect a time variation of it at the same distance from the core over 7 yr. We discuss the origin of the Faraday rotation based on this rapid time variation. We rule out foreground media such as a narrow-line region, and suggest a helical magnetic field in the sheath region as the origin of this gradient of the RM.

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Title: Hubble Space Telescope far-ultraviolet imaging of the jet in 3C273: a common emission component from optical to X-rays
Authors: Sebastian Jester (1,2), Klaus Meisenheimer (1), Andre' Martel (3), Eric Perlman (4), Bill Sparks (5) ((1) MPIA Heidelberg, (2) Fermilab Particle Astrophysics Center, (3) JHU, (4) FIT, (5) STScI)

We present far-ultraviolet (UV) observations at 150 nm of the jet of the quasar 3C 273 obtained with the Advanced Camera for Survey's Solar Blind Channel (ACS/SBC) on board the Hubble Space Telescope. While the jet morphology is very similar to that in the optical and near-ultraviolet, the spectral energy distributions (SEDs) of the jet's sub-regions show an upturn in nu f_nu at 150 nm compared to 300 nm everywhere in the jet. Moreover, the 150 nm flux is compatible with extrapolating the X-ray power-law down to the ultra-violet region. This constitutes strong support for a common origin of the jet's far-UV and X-ray emission. It implies that even a substantial fraction of the *visible light* in the X-ray brightest parts of the jet arises from the same spectral component as the X-rays, as had been suggested earlier based on Spitzer Space Telescope observations. We argue that the identification of this UV/X-ray component opens up the possibility to establish the synchrotron origin of the X-ray emission by optical polarimetry.

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3C Quasars and Radio Galaxies
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Title: Spitzer Observations of 3C Quasars and Radio Galaxies: Mid-Infrared Properties of Powerful Radio Sources
Authors: K. Cleary (1), C.R. Lawrence (1), J.A. Marshall (2), L. Hao (2), D. Meier (1) ((1) Jet Propulsion Laboratory, California Institute of Technology, (2) Cornell University)

We have measured mid-infrared radiation from an orientation-unbiased sample of 3CRR galaxies and quasars at redshifts 0.4 < z < 1.2 with the IRS and MIPS instruments on the Spitzer Space Telescope. Powerful emission (L_24µ > 10˛˛.4 W/Hz/sr) was detected from all but one of the sources. We fit the Spitzer data as well as other measurements from the literature with synchrotron and dust components. The IRS data provide powerful constraints on the fits. At 15 microns, quasars are typically four times brighter than radio galaxies with the same isotropic radio power. Based on our fits, half of this difference can be attributed to the presence of non-thermal emission in the quasars but not the radio galaxies. The other half is consistent with dust absorption in the radio galaxies but not the quasars. Fitted optical depths are anti-correlated with core dominance, from which we infer an equatorial distribution of dust around the central engine. The median optical depth at 9.7 microns for objects with core-dominance factor R > 10^-2 is approximately 0.4; for objects with R < 10^-2, it is 1.1. We have thus addressed a long-standing question in the unification of FR II quasars and galaxies: quasars are more luminous in the mid-infrared than galaxies because of a combination of Doppler-boosted synchrotron emission in quasars and extinction in galaxies, both orientation-dependent effects.

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A new false-coloured image from NASA's Hubble, Chandra, and Spitzer space telescopes shows a giant jet of particles that has been shot out from the vicinity of a type of supermassive black hole called a quasar. The jet is enormous, stretching across more than 100,000 light-years of space -- a size comparable to our own Milky Way galaxy.

3C273
Credit nasa

The jet pictured here is streaming out from the first known quasar, called 3C273, discovered in 1963. A kaleidoscope of colours represents the jet's assorted light waves. X-rays, the highest-energy light in the image, are shown at the far left in blue (the black hole itself is well to the left of the image). The X-rays were captured by Chandra. As you move from left to right, the light diminishes in energy, and wavelengths increase in size. Visible light recorded by Hubble is displayed in green, while infrared light caught by Spitzer is red. Areas where visible and infrared light overlap appear yellow.

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-- Edited by Blobrana at 18:35, 2006-07-24

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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 centre 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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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.

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. These combined data strongly suggest that ultra-energetic particles in the 3C273 jet are producing their light via synchrotron radiation." - C. Megan Urry, Israel Munson Professor of Physics and Astronomy at Yale, and an author on one study.

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. 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." - Sebastian Jester

"Our results call for a radical rethink of the physics of relativistic jets that black holes drive. But, we now have a crucial new clue to solving one of the major mysteries in high-energy astrophysics." - Yasunobu Uchiyama.

(see above post)

Source: Yale University

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Title: Shedding New Light on the 3C 273 Jet with the Spitzer Space Telescope
Authors: Y. Uchiyama, C. M. Urry, C. C. Cheung, S. Jester, J. Van Duyne, P. Coppi, R. M. Sambruna, T. Takahashi, F. Tavecchio, L. Maraschi

Researchers have performed infrared imaging of the jet of the quasar 3C 273 at wavelengths 3.6 and 5.8 microns with the Infrared Array Camera (IRAC) on the Spitzer Space Telescope.
When combined with the radio, optical and X-ray measurements, the IRAC photometry clearly shows that the optical emission is dominated by the high-energy component of the jet, not by the radio synchrotron component, as had been assumed to date.
The high-energy component may be due to a second synchrotron component or to IC scattering of ambient photons. In the former case, they argue that the acceleration of protons exceeding 10^16 eV or possibly even to 10^19 eV would be taking place in the jet. In contrast, the IC model, into which highly relativistic Doppler beaming has to be incorporated, requires very low-energy electrons (~ 1 MeV). The present polarisation data in the radio and optical would favour the former interpretation in the case of the 3C 273 jet.
Sensitive and detailed measurements of optical polarisation are important to establish the radiation mechanism responsible for the high-energy emission. The present study offers new clues as to the controversial origin of the X-ray emission seen in many quasar jets.

3C 273

Spitzer-HST-Chandra composite image of the jet of 3C 273. The colours are coded as follows: Spitzer “deconvolved" 3.6 µm (red), HST “UV excess" f0.3µm -0.05× f1.6µm (green), Chandra 0.4–6 keV (blue). The VLA radio (2 cm) contours are superposed on the image, with the strongest radio source H2 being truncated. There are two distinct types of radiating knots; the inner knots show hard optical spectra (green) and strong X-rays (blue) while the outer knots show
bright infrared (red).


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