Shedding New Light on the 3C 273 Jet With the Spitzer Space Telescope (original) (raw)
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The Astrophysical Journal, 2012
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multiwavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported γ-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the γ-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated by ∼ 90 days, with only weak γ-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the γ-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the γ-ray flaring event by a shift of its location from ∼ 1 pc to ∼ 4 pc from the central black hole. On the other hand, if the γ-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.
We present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the gamma-ray emission by about 10 days. X-ray observations reveal a pair of `isolated' flares separated by ~90 days, with only weak gamma-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the gamma-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the ...
Astrophysical Journal, 2006
The process responsible for the Chandra-detected X-ray emission from the large scale jets of powerful quasars is a matter of ongoing debate. The two main contenders are external Compton (EC) scattering off the cosmic microwave background (CMB) photons (EC/CMB) and synchrotron emission from a population of electrons separate from those producing the radio -IR emission. So far, no clear diagnostics have been presented to distinguish which of the two, if any, is the actual X-ray emission mechanism. Here we present such diagnostics based on a fundamental difference between these two models: the production of synchrotron X-rays requires multi -TeV electrons, while the EC/CMB model requires a cutoff in the electron energy distribution (EED) below TeV energies. This has significant implications for the γ-ray emission predicted by these two models, that can be tested through GeV and TeV observations of the nearby bright quasar 3C 273. We show how existing and future GeV and TeV observations can confirm or refute one or both of the above hypotheses.
Possible proton synchrotron origin of X-ray and gamma-ray emission in large-scale jet of 3C 273
Monthly Notices of the Royal Astronomical Society: Letters
The large-scale jet of quasar 3C 273 has been observed in radio to gamma-ray frequencies. Earlier the X-ray emission from knot A of this jet has been explained with inverse Compton scattering of the cosmic microwave background radiations by the shock accelerated relativistic electrons in the jet. More recently it has been shown that this mechanism overproduces the gamma-ray flux at GeV energy and violates the observational results from Fermi LAT. We have considered the synchrotron emission from a broken power-law spectrum of accelerated protons in the jet to explain the observed X-ray to gamma-ray flux from knot A. The two scenarios discussed in our work are (i) magnetic field is high, synchrotron energy loss time of the protons is shorter than their escape time from the knot region and the age of the jet and (ii) their escape time is shorter than their synchrotron energy loss time and the age of the jet. These scenarios can explain the observed photon spectrum well for moderate values of Doppler factor. The required jet luminosity is high ∼10 46 erg s −1 in the first scenario and moderate ∼10 45 erg s −1 in the second, which makes the second scenario more favourable.
Possible Proton Synchrotron Origin of X-Ray & Gamma Ray Emission in Large Scale Jet of 3C 273
MNRAS Letters
The large scale jet of quasar 3C 273 has been observed in radio to γ ray frequencies. Earlier the X-ray emission from knot A of this jet has been explained with inverse Compton scattering of the cosmic microwave background radiations by the shock accelerated relativistic electrons in the jet. More recently it has been shown that this mechanism overproduces the gamma ray flux at GeV energy and violates the observational results from Fermi LAT. We have considered the synchrotron emission from a broken power law spectrum of accelerated protons in the jet to explain the observed X-ray to γ ray flux from knot A. The two scenarios discussed in our work are (i) magnetic field is high, synchrotron energy loss time of the protons is shorter than their escape time from the knot region and the age of the jet (ii) their escape time is shorter than their synchrotron energy loss time and the age of the jet. These scenarios can explain the observed photon spectrum well for moderate values of Doppler factor. The required jet luminosity is high ∼ 10 46 erg/sec in the first scenario and moderate ∼ 10 45 erg/sec in the second, which makes the second scenario more favorable.
PROTON SYNCHROTRON RADIATION FROM EXTENDED JETS OF PKS 0637-752 AND 3C 273
PROTON SYNCHROTRON RADIATION FROM EXTENDED JETS OF PKS 0637–752 AND 3C 273, 2016
Many powerful radio quasars are associated with large-scale jets, exhibiting bright knots as shown by high-resolution images from the Hubble Space Telescope (HST) and the Chandra X-ray Observatory. The radio-optical flux component from these jets can be attributed to synchrotron radiation by accelerated relativistic electrons while the IC/CMB model, by far, has been the most popular explanation for the observed X-ray emission from these jets. Recently, the IC/CMB X-ray mechanism has been strongly disfavored for 3C 273 and PKS 0637-752 since the anomalously hard and steady gamma-ray emission predicted by such models violates the observational results from Fermi-LAT. Here we propose the proton synchrotron origin of the X-ray-gamma-ray flux from the knots of PKS 0637-752 with a reasonable budget in luminosity, by considering synchrotron radiation from an accelerated proton population. Moreover, for the source 3C 273, the optical data points near 10 15 Hz could not be fitted using electron synchrotron. We propose an updated proton synchrotron model, including the optical data from HST, to explain the common origin of optical-X-ray-gamma-ray emission from the knots of quasar 3C 273 as an extension of the work done by Kundu & Gupta. We also show that TeV emission from large-scale quasar jets, in principle, can arise from proton synchrotron, which we discuss in the context of knot wk8.9 of PKS 0637-752.
The surprising nature of kpc-scale quasar jets as revealed by gamma-ray observations
Proceedings of 10th INTEGRAL Workshop: A Synergistic View of the High-Energy Sky — PoS(Integral2014)
The physical origin of the X-ray emssion from radio knots in powerful quasar jets has been a long-standing mystery. Though we know that these jets start out on the sub-pc scale as highly relativistic flows, we do not have any direct measurement of their speeds on the kpc scale, where the vast distances from the core necessitate in situ particle acceleration. If the jets remain highly relativistic, then the X-rays could be due to inverse-Compton upscattering of CMB photons. However, the IC/CMB explanation also predicts a high level of gamma-ray emission. Our recent work shows that this emission is not seen to a very high significance (>99.9% confidence) in at least two sources, 3C 273 and PKS 0637-752. Further, our findings suggest that these jets are not highly relativistic and that the X-rays are synchrotron in origin. I will discuss some of the surprising implications of these findings for the energetics and radiative output of powerful quasars.