High-Resolution Three-dimensional Simulations of Relativistic Jets

Aloy, M. Á.; Ibáñez, Javier; Martí, Juan José Ibàñez; Gómez, J. L.; Müller, Ewald

doi:10.1086/312266

Cited by 103 publications

(108 citation statements)

References 17 publications

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“…Yet the exact velocity structure both along and across large-scale jets in FR II radio galaxies and quasars remains an open issue. The strong terminal shocks at the hot spots are unlikely to be moving with high bulk Lorentz factors, but moderately relativistic motions (À blk a few) are permitted by hydrodynamic simulations (e.g., Aloy et al 1999). We note that such simulations repeatedly reveal a complex hot spot morphology, especially at the late stages of the jet evolution (e.g., Martí et al 1997;Mizuta et al 2004).…”

Section: Introductionmentioning

confidence: 81%

X‐Ray Emission Properties of Large‐Scale Jets, Hot Spots, and Lobes in Active Galactic Nuclei

Kataoka

Stawarz

2005

ApJ

237

269

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We examine a systematic comparison of jet knots, hot spots, and radio lobes recently observed with Chandra and ASCA. This report discusses the origin of their X-ray emissions and investigates the dynamics of the jets. The data were compiled at well-sampled radio (5 GHz) and X-ray (1 keV ) frequencies for more than 40 radio galaxies. We examine three models for the X-ray production: synchrotron (SYN), synchrotron self-Compton (SSC), and external Compton ( EC) on cosmic microwave background (CMB) photons. For the SYN sources-mostly jet knots in nearby low-luminosity radio galaxies-X-ray photons are produced by ultrarelativistic electrons with energies 10-100 TeV that must be accelerated in situ. For the other objects, conservatively classified as SSC or EC sources, a simple formulation of calculating the ''expected'' X-ray fluxes under an equipartition hypothesis is presented. We confirm that the observed X-ray fluxes are close to the expected ones for nonrelativistic emitting plasma velocities in the case of radio lobes and the majority of hot spots, whereas a considerable fraction of jet knots are too bright in X-rays to be explained in this way. We examine two possibilities to account for the discrepancy in a framework of the inverse Compton model: (1) the magnetic field is much smaller than the equipartition value, and (2) the jets are highly relativistic on kiloparsec and megaparsec scales. We conclude that if the inverse Compton model is the case, the X-ray-bright jet knots are most likely far from the minimum-power condition. We also briefly discuss the other possibility, namely, that the observed X-ray emission from all the jet knots is synchrotron in origin.

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Section: Introductionmentioning

confidence: 81%

X‐Ray Emission Properties of Large‐Scale Jets, Hot Spots, and Lobes in Active Galactic Nuclei

Kataoka

Stawarz

2005

ApJ

237

269

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“…Numerical simulations of supersonic jets in two and three dimensions (e.g., Aloy et al 1999;Norman 1996;Komissarov & Falle 1996;Tregillis et al 2001) suggest that flow speeds in and around hotspots can be much larger than those expected from the one-dimensional strong shock model, because the shock structure at the jet termination is more complex than a single terminal Mach disk. The simulated jets undergo violent structural and velocity changes near the jet head due to pressure variations in the turbulent cocoon.…”

Section: Arguments For Doppler Beamingmentioning

confidence: 99%

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

Godfrey

Bicknell

Lovell

et al. 2009

ApJ

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Long Baseline Array imaging of the z = 0.663 broadline radio galaxy PKS 1421−490 reveals a 400 pc diameter high surface brightness hot spot at a projected distance of ∼40 kpc from the active galactic nucleus. The isotropic X-ray luminosity of the hot spot, L 2-10 keV = 3 × 10 44 ergs s −1 , is comparable to the isotropic X-ray luminosity of the entire X-ray jet of PKS 0637−752, and the peak radio surface brightness is hundreds of times greater than that of the brightest hot spot in Cygnus A. We model the radio to X-ray spectral energy distribution using a one-zone synchrotron self-Compton model with a near equipartition magnetic field strength of 3 mG. There is a strong brightness asymmetry between the approaching and receding hotspots and the hot spot spectrum remains flat (α ≈ 0.5) well beyond the predicted cooling break for a 3 mG magnetic field, indicating that the hotspot emission may be Doppler beamed. A high plasma velocity beyond the terminal jet shock could be the result of a dynamically important magnetic field in the jet. There is a change in the slope of the hotspot radio spectrum at GHz frequencies, which we model by incorporating a cutoff in the electron energy distribution at γ min ≈ 650, with higher values implied if the hotspot emission is Doppler beamed. We show that a sharp decrease in the electron number density below a Lorentz factor of 650 would arise from the dissipation of bulk kinetic energy in an electron/proton jet with a Lorentz factor Γ jet 5.

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“…In addition, a detailed analysis of the broad-band emission of several other quasar jets supports the synchrotron hypothesis, pointing out an important role of the jet velocity structure (consisting of a fast spine and a slower boundary layer/outer sheath) in shaping the jet high-energy radiation (e.g., Hardcastle 2006, Jester et al 2006. Such jet velocity structure is in fact always seen in numerical modeling of the evolution and propagation of extragalactic relativistic jets (e.g., Aloy et al 1999, Leismann et al 2005, Mizuno et al 2007, since it results inevitably from the non-linear growth of Kelvin-Helmholtz instabilities on the jet surface (see the recent studies by Perucho et al 2007, Hardee 2007, Meliani & Keppens 2007, and references therein). It is not yet established, however, if the jet boundary layers are indeed the places of the enhanced acceleration of high-energy particles.…”

Section: Introductionmentioning

confidence: 62%

Chandra Reveals Twin X-ray Jets in the Powerful FR II Radio Galaxy 3C 353

Kataoka

2008

AIP Conference Proceedings

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We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-ray Observatory. 3C 353's two 4 ′′ -wide and 2 ′ -long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution provided by the VLA and Chandra instruments. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C 353, including the nucleus, the jet and the counterjet, the terminal jet regions (hotspots), and one radio lobe. We show that the detection of the X-ray emission associated with the radio knots and counterknots, which is most likely non-thermal in origin, puts several crucial constraints on the X-ray emission mechanisms in powerful large-scale jets of quasars and FR II sources. In particular, we show that this detection is inconsistent with the inverse-Compton model proposed in the literature, and instead implies a synchrotron origin of the X-ray jet photons. We also find that the width of the X-ray counterjet is possibly narrower than that measured in radio bands, that the radio-to-X-ray flux ratio decreases systematically downstream along the jets, and that there are substantial (kpc-scale) offsets between the positions of the X-ray and radio intensity maxima within each knot, whose magnitudes increase away from the nucleus. We discuss all these findings in the wider context of the physics of extragalactic jets, proposing some particular though not definitive solutions or interpretations for each problem. In general, we find that the synchrotron X-ray emission of extragalactic large-scale jets is not only shaped by the global hydrodynamical configuration of the outflows, but is also likely to be very sensitive to the microscopic parameters of the jet plasma. A complete, self-consistent model for the X-ray emission of extragalactic jets still remains elusive.

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High-Resolution Three-dimensional Simulations of Relativistic Jets

Cited by 103 publications

References 17 publications

X‐Ray Emission Properties of Large‐Scale Jets, Hot Spots, and Lobes in Active Galactic Nuclei

X‐Ray Emission Properties of Large‐Scale Jets, Hot Spots, and Lobes in Active Galactic Nuclei

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

Chandra Reveals Twin X-ray Jets in the Powerful FR II Radio Galaxy 3C 353

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