Large-scale Jet Research Articles

Radio structure of the blazar 1156 + 295 with sub-pc resolution

1156+295 is a flat-spectrum quasar which is loud at radio and gamma-ray. Previous observations of the source revealed a radio morphology on pc to kpc scales consistent with a helical jet model. In our present research, this source was observed with the VLBA at 86, 43 and 15 GHz on four epochs from 10 May 2003 to 13 March 2005 aiming at studying the structure of the innermost jet in order to understand the relation between the helical structure and the astrophysical processes in the central engine. A core-jet structure with six jet components is identified. The apparent transverse velocities of the six jet components derived from proper motion measurements are in the range between 3.6 c and 11.6 c. The overall jet shape shows oscillatory morphology with multiple curvatures on pc scales which might be indicative of a helical pattern. Models of helical jet are discussed on the basis of both Kelvin-Helmholtz (K-H) instability and jet precession. The K-H instability model shows better agreement with the observed data. The overall radio structure on the scale from sub-pc to kpc appears to be fitted with a hydrodynamic model with the fundamental helical mode in Kelvin-Helmholtz (K-H) instability. This helical mode with an initial characteristic wavelength of 0.2 pc is excited at the base of the jet on the scale of 0.005 pc (or 1000R_s, the typical size of the broad line region for a super massive black hole of $4.3\times10^8M_{\odot}$). A presessing jet model can also fit the observed jet structure on the scale between 10 pc and 300 pc. However, additional astrophysical processes may be required for the presessing jet model in order to explain the bendings on the inner jet structure (1 to 10 pc) and re-collimation of the large scale jet outflow (>300 pc).

Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004

We study the jet kinematics of the blazar S5 0716+714 during its active state in 2003-2004 with multi-epoch VLBI observations. Aims. We present a kinematic analysis of the large-scale (0-12 mas) jet of 0716+714, based on the results of six epochs of VLBA monitoring at 5 GHz. Additionally, we compare kinematic results obtained with two imaging methods based on different deconvolution algorithms. The blazar 0716+714 has a diffuse large-scale jet and a very faint bright compact core. Experiments with simulated data showed that the conventional data reduction procedure based on the CLEAN deconvolution algorithm does not perform well in restoring this type of structure. This might be the reason why previous kinematic studies of this source yielded ambiguous results. In order to obtain accurate kinematics of this source, we independently applied two imaging techniques to the raw data: the conventional method, based on difference mapping, which uses CLEAN deconvolution, and the generalized maximum entropy method (GMEM) realized in the VLBImager package developed at the Pulkovo Observatory in Russia. The results of both methods give us a consistent kinematic scenario: the large-scale jet of 0716+714 is diffuse and stationary. Differences between the inner (0-1 mas) and outer (1-12 mas) regions of the jet in brightness and velocity of the components could be explained by the bending of the jet, which causes the angle between the jet direction and the line of sight to change from ~5 deg to ~11 deg. For the source 0716+714 both methods worked at the limit of their capability.

On the source of dense outflows from T Tauri stars - III. Winds driven from the star-disc shear layer

Ultraviolet observations of classical T Tauri Stars (cTTSs) have shown that there is a hot (Te≃ 80 000 K) and dense (ne≃ 1010 cm−3) component associated with the large-scale jet. This hot component is formed very close to the base of the jet providing fundamental information on the jet formation mechanism. In this series, we have investigated whether this component can be formed in disc winds, either cool or warm. To conclude the series, jet launching from the interface between the magnetic rotor (the star) and the disc is studied. Synthetic profiles are calculated from numerical simulations of outflow launching by star–disc interaction. Profiles are calculated for several possible configurations of the stellar field: dipolar (with surface strengths B* of 1, 2 and 5 kG) or dynamo fed. Also two types of discs, passive or subjected to an αΩ-dynamo, are considered. These profiles have been used to define the locus of the various models in the observational diagram: dispersion versus centroid, for the profiles of the Si iii] line. Bulk motions produce an increasing broadening of the profile as the lever arm launching the jet becomes more efficient; predicted profiles are however sensitive to the disc inclination. Models are compared with observations of the Si iii] lines obtained with the Hubble Space Telescope. In addition, it is shown that the non-stationary nature of star–disc winds produce a flickering of the profile during quiescence with variations in the line flux of about 10 per cent. At outburst, accretion signatures appear in the profiles together with an enhancement of the wind, producing the correlation between accretion and outflow as reported from RU Lup, AA Tau and RW Aur observations.

Stability of three-dimensional relativistic jets: implications for jet collimation

The stable propagation of jets in FRII sources is remarkable if one takes into account that large-scale jets are subjected to potentially highly disruptive three-dimensional (3D) Kelvin-Helmholtz instabilities. Numerical simulations can address this problem and help clarify the causes of this remarkable stability. Following previous studies of the stability of relativistic flows in two dimensions (2D), it is our aim to test and extend the conclusions of such works to three dimensions. We present numerical simulations for the study of the stability properties of 3D, sheared, relativistic flows. This work uses a fully parallelized code Ratpenat that solves equations of relativistic hydrodynamics in 3D. The results of the present simulations confirm those in 2D. We conclude that the growth of resonant modes in sheared relativistic flows could be important in explaining the long-term collimation of extragalactic jets.

Parabolized stability equation models of large-scale jet mixing noise

models to predict the evolution of low frequencies, large-scale wavepacket structures in turbulent jets and their radiated sound. We consider computations and data corresponding to high subsonic and supersonic jets from circular nozzles. Previous methods are extended to consider nonlinear interactions amongst the waves and use a Kirchhoff-surface type approach to project the near-field wavepacket amplitudes to the far-field. Linear PSE, whose initial conditions are chosen to provide an overall amplitude reference, show excellent agreement for the wavepacket amplitudes and phases with microphone array data just outside the jet shear layers, especially when the microphone data are processed to filter out contributions from uncorrelated fluctuations. Far-field sound predictions based on the linear PSE are also in reasonable agreement with far-field data. In order to investigate nonlinearity, we use an LES database to evaluate initial conditions for the PSE modes, and then compare their later evolution along the jet. Preliminary cases show some sensitivity to the initial amplitudes and their phases, and that nonlinear effects may be important in predicting the far-field sound based on the initial (near-nozzle) spectrum of disturbances.

Reprint of: Parabolized stability equation models of large-scale jet mixing noise

We report on the development of parabolized stability equation models to predict the evolution of low frequencies, large-scale wavepacket structures in turbulent jets and their radiated sound. We consider computations and data corresponding to high subsonic and supersonic jets from circular nozzles. Previous methods are extended to consider nonlinear interactions amongst the waves and use a Kirchhoff-surface type approach to project the near-field wavepacket amplitudes to the far-field. Linear PSE, whose initial conditions are chosen to provide an overall amplitude reference, show excellent agreement for the wavepacket amplitudes and phases with microphone array data just outside the jet shear layers, especially when the microphone data are processed to filter out contributions from uncorrelated fluctuations. Far-field sound predictions based on the linear PSE are also in reasonable agreement with far-field data. In order to investigate nonlinearity, we use an LES database to evaluate initial conditions for the PSE modes, and then compare their later evolution along the jet. Preliminary cases show some sensitivity to the initial amplitudes and their phases, and that nonlinear effects may be important in predicting the far-field sound based on the initial (near-nozzle) spectrum of disturbances.

Properties of large-scale methane/hydrogen jet fires

A future economy based on reduction of carbon-based fuels for power generation and transportation may consider hydrogen as possible energy carrier. Extensive and widespread use of hydrogen might require a pipeline network. The alternatives might be the use of the existing natural gas network or to design a dedicated network. Whatever the solution, mixing hydrogen with natural gas will modify the consequences of accidents, substantially. The French National Research Agency (ANR) funded project called HYDROMEL focuses on these critical questions. Within this project large-scale jet fires have been studied experimentally and numerically. The main characteristics of these flames including visible length, radiation fluxes and blowout have been assessed.

Stochastic Subgrid Parameterizations for Simulations of Atmospheric Baroclinic Flows

AbstractA stochastic subgrid modeling method is used to parameterize horizontal and vertical subgrid-scale transfers in large-eddy simulations (LESs) of baroclinic flows with large-scale jets and energy spectra typical of the atmosphere. The approach represents the subgrid-scale eddies for LES (at resolutions of T63 and T31) by a stochastic model that takes into account the memory effects of turbulent eddies. The statistics of the model are determined from a higher-resolution (T126) direct numerical simulation (DNS). The simulations use a quasigeostrophic two-level model and the subgrid terms are inhomogeneous in the vertical and anisotropic in the horizontal and are represented by 2 × 2 matrices at each wavenumber. The parameterizations have the largest magnitudes at a cusp near the largest total wavenumbers of the truncations. At T63 the off-diagonal elements of the matrices are negligible (corresponding to effectively decoupled levels) and the diagonal elements are almost isotropic. At the lower resolution of T31 the off-diagonal elements are more important and even the diagonal elements are more anisotropic. At both resolutions, and for anisotropic or isotropized subgrid terms, LESs are in excellent agreement with higher-resolution DNS.

Low-level jet development and the interaction of different scale physical processes

Two cases of low-level jet events and the interaction of the involved physical processes are investigated. The vertical distribution of the dominant atmospheric motions is studied, using data from a SODAR-RASS system and in situ instrumentation, at a coastal region of the Eastern Mediterranean (Messogia Plain in Attica—Greece). The first low-level jet (LLJ) case was observed during the cold period, after the passage of a cold front and could be characterized as purely synoptic. Coherent inertial motions were found to follow the frontal surface at both the wind components, with larger amplitudes at the alongfront wind component, a fact consistent with the deformation theory. The contribution of the diurnal cycle was found weak in both the components, due to the cloudiness and the small diurnal temperature range, while the synoptic scale dominated the northerly wind component. The second LLJ case represents two successive summertime large-scale jets. The absence of cloudiness and the increased solar radiation provided a favorable environment for the development of local flows which interacted with the synoptic wind field. This interaction led to a LLJ with an oscillating core and a variable depth. The diurnal cycle had a strong imprint on the wind component along the sea breeze direction (easterly), while the synoptic variations dominated the northerly wind component. Strong amplitudes of a coherent quasi 2-day variation were also found in both the cases.

A modified stratified model for the 3C 273 jet

We present a modified stratified jet model to interpret the observed spectral energy distributions of knots in the 3C 273 jet. Based on the hypothesis of the single index of the particle energy spectrum at injection and identical emission processes among all the knots, the observed difference of spectral shape among different 3C 273 knots can be understood as a manifestation of the deviation of the equivalent Doppler factor of stratified emission regions in an individual knot from a characteristic one. The summed spectral energy distributions of all ten knots in the 3C 273 jet can be well fitted by two components: a low-energy component (radio to optical) dominated by synchrotron radiation and a high-energy component (UV, X-ray and γ-ray) dominated by inverse Compton scattering of the cosmic microwave background. This gives a consistent spectral index of α = 0.88 (Sv ∝ v−α) and a characteristic Doppler factor of 7.4. Assuming the average of the summed spectrum as the characteristic spectrum of each knot in the 3C 273 jet, we further get a distribution of Doppler factors. We discuss the possible implications of these results for the physical properties in the 3C 273 jet. Future GeV observations with GLAST could separate the γ-ray emission of 3C 273 from the large scale jet and the small scale jet (i.e. the core) through measuring the GeV spectrum.

Determination of the intrinsic velocity field in the M87 jet

A new method to estimate the Doppler beaming factor of relativistic large-scale jet regions is presented. It is based on multiwaveband fitting to radio-to-X-ray continua with synchrotron spectrum models. Combining our method with available observational data of proper motions, we derive the intrinsic velocity as well as the viewing angles to the line of sight for eight knotty regions down the M87 jet. The results favour the ‘modest beaming’ scenario along the jet, with Doppler factors varying between ∼2–5. The inner jet of M87 suffers sharp deceleration, and the intrinsic speed remains roughly constant down the outer jet. The orientation of the inner jet regions is fully consistent with the result of 10 ◦ –19 ◦ to the line of sight suggested by previous Hubble Space Telescope (HST) proper motion studies of the M87 jet. The outer jet, however, shows systematic deflection off the inner jet to a much smaller inclination (θ � 10 ◦ ). Further calculation of knot A suggests that this deflection can be regarded as evidence that the outer jet suffers some departure from equipartition. The nucleus region of the M87 jet should have a viewing angle close to its first knot HST-1, i.e. θ ∼ 15 ◦ , which favours the idea that M87 may be a misaligned blazar. This work provides some hints about the overall dynamics of this famous extragalactic jet.

Analysis of jet flames and unignited jets from unintended releases of hydrogen

Abstract A combined experimental and modeling program is being carried out at Sandia National Laboratories to characterize and predict the behavior of unintended hydrogen releases. In the case where the hydrogen leak remains unignited, knowledge of the concentration field and flammability envelope is an issue of importance in determining consequence distances for the safe use of hydrogen. In the case where a high-pressure leak of hydrogen is ignited, a classic turbulent jet flame forms. Knowledge of the flame length and thermal radiation heat flux distribution is important to safety. Depending on the effective diameter of the leak and the tank source pressure, free jet flames can be extensive in length and pose significant radiation and impingement hazard, resulting in consequence distances that are unacceptably large. One possible mitigation strategy to potentially reduce the exposure to jet flames is to incorporate barriers around hydrogen storage equipment. The reasoning is that walls will reduce the extent of unacceptable consequences due to jet releases resulting from accidents involving high-pressure equipment. While reducing the jet extent, the walls may introduce other hazards if not configured properly. The goal of this work is to provide guidance on configuration and placement of these walls to minimize overall hazards using a quantitative risk assessment approach. The program includes detailed CFD calculations of jet flames and unignited jets to predict how hydrogen leaks and jet flames interact with barriers, complemented by an experimental validation program that considers the interaction of jet flames and unignited jets with barriers. As a first step in this work on barrier release interaction the Sandia CFD model has been validated by computing the concentration decay of unignited turbulent free jets and comparing the results with the classic concentration decay laws for turbulent free jets taken from experimental data. Computations for turbulent hydrogen free jet flames are also presented and compared with experimental data for the temperature profile in lab-scale turbulent free hydrogen jet flames. Finally, preliminary results of calculations of hydrogen jet flame impingement on barriers are presented and compared with images of large-scale hydrogen jet flame deflection from barrier wall experimental tests.

FORMATION OF PROTOSTELLAR JETS AS TWO-COMPONENT OUTFLOWS FROM STAR-DISK MAGNETOSPHERES

Axisymmetric magnetohydrodynamic (MHD) simulations have been applied to investigate the interrelation of a central stellar magnetosphere and stellar wind with a surrounding magnetized disk outflow and how the overall formation of a large scale jet is affected. The initial magnetic field distribution applied is a superposition of two components - a stellar dipole and a surrounding disk magnetic field, in both either parallel or anti-parallel alignment. Correspondingly, the mass outflow is launched as stellar wind plus a disk wind. Our simulations evolve from an initial state in hydrostatic equilibrium and an initially force-free magnetic field configuration. Due to initial differential rotation and induction of a strong toroidal magnetic field the stellar dipolar field inflates and is disrupted on large scale. Stellar and disk wind may evolve in a pair of collimated outflows. The existence of a reasonably strong disk wind component is essential for collimation. A disk jet as known from previous numerical studies will become de-collimated by the stellar wind. In some simulations we observe the generation of strong flares triggering a sudden change in the outflow mass loss rate by a factor of two and also a re-distribution in the radial profile of momentum flux and jet velocity across the jet. We discuss the hypothesis that these flares may trigger internal shocks in the asymptotic jets which are observed as knots.

The X-ray jets of active galaxies

Jet physics is again flourishing as a result of Chandra’s ability to resolve high-energy emission from the radio-emitting structures of active galaxies and separate it from the X-ray-emitting thermal environments of the jets. These enhanced capabilities have coincided with an increasing interest in the link between the growth of super-massive black holes and galaxies, and an appreciation of the likely importance of jets in feedback processes. I review the progress that has been made using Chandra and XMM-Newton observations of jets and the medium in which they propagate, addressing several important questions, including: Are the radio structures in a state of minimum energy? Do powerful large-scale jets have fast spinal speeds? What keeps jets collimated? Where and how does particle acceleration occur? What is jet plasma made of? What does X-ray emission tell us about the dynamics and energetics of radio plasma/gas interactions? Is a jet’s fate determined by the central engine?

LES of high pressure hydrogen jet fire

This work describes a large eddy simulation (LES) approach to model high pressure jet fires. Numerical simulations are compared against a large scale vertical, hydrogen jet fire test [Schefer, R. W., Houf, W. G., Williams, T. C., Bourne, B., & Colton, J. (2007). Characterization of high-pressure, under-expanded hydrogen-jet flames. International Journal of Hydrogen Energy, 32(12), 2081–2093], which gives experimental data for blowdown from a tank at an initial pressure of 413 bar through a 5.08 mm diameter nozzle. In this work, conditions 5 s after the start of the release have been taken to simulate a “quasi-steady” state. The work was driven by the need to develop contemporary tools for safety assessment of real scale under-expanded hydrogen jet fires and an aim was to study an LES model performance to reproduce such large scale jet fires in an industrial safety context. Detailed simulations of the flow structure in under-expanded part of the jet are avoided in this work using the notional nozzle concept. The LES combustion model is based on the mixture fraction approach and probability density function to account for flame–turbulence interaction. A flamelet library of the relationship between the instantaneous composition of the reacting mixture and the mixture fraction is calculated in advance. A comparison of experimental observations and simulation results (flame length, flame width) is discussed in view of the grid resolution required for LES and boundary conditions such as turbulence intensity and turbulent length scale at the notional nozzle.

Formation of Jets by Baroclinic Turbulence

Abstract Turbulent fluids are frequently observed to spontaneously self-organize into large spatial-scale jets; geophysical examples of this phenomenon include the Jovian banded winds and the earth’s polar-front jet. These relatively steady large-scale jets arise from and are maintained by the smaller spatial- and temporal-scale turbulence with which they coexist. Frequently these jets are found to be adjusted into marginally stable states that support large transient growth. In this work, a comprehensive theory for the interaction of jets with turbulence, stochastic structural stability theory (SSST), is applied to the two-layer baroclinic model with the object of elucidating the physical mechanism producing and maintaining baroclinic jets, understanding how jet amplitude, structure, and spacing is controlled, understanding the role of parameters such as the temperature gradient and static stability in determining jet structure, understanding the phenomenon of abrupt reorganization of jet structure as a function of parameter change, and understanding the general mechanism by which turbulent jets adjust to marginally stable states supporting large transient growth. When the mean thermal forcing is weak so that the mean jet is stable in the absence of turbulence, jets emerge as an instability of the coupled system consisting of the mean jet dynamics and the ensemble mean eddy dynamics. Destabilization of this SSST coupled system occurs as a critical turbulence level is exceeded. At supercritical turbulence levels the unstable jet grows, at first exponentially, but eventually equilibrates nonlinearly into stable states of mutual adjustment between the mean flow and turbulence. The jet structure, amplitude, and spacing can be inferred from these equilibria. With weak mean thermal forcing and weak but supercritical turbulence levels, the equilibrium jet structure is nearly barotropic. Under strong mean thermal forcing, so that the mean jet is unstable in the absence of turbulence, marginally stable highly nonnormal equilibria emerge that support high transient growth and produce power-law relations between, for example, heat flux and temperature gradient. The origin of this power-law behavior can be traced to the nonnormality of the adjusted states. As the stochastic excitation, mean baroclinic forcing, or the static stability are changed, meridionally confined jets that are in equilibrium at a given meridional wavenumber abruptly reorganize to another meridional wavenumber at critical values of these parameters. The equilibrium jets obtained with this theory are in remarkable agreement with equilibrium jets obtained in simulations of baroclinic turbulence, and the phenomenon of discontinuous reorganization of confined jets has important implications for storm-track reorganization and abrupt climate change.

ChandraReveals Twin X‐Ray Jets in the Powerful FR II Radio Galaxy 3C 353

We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-Ray Observatory. Due to 3C 353's two -->4' ' wide and -->2' long jets we are able to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the subarcsecond 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 (hot spots), 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 nonthermal 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 although 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.

A Kiloparsec‐Scale X‐Ray Jet in the BL Lac Source S5 2007+777

X-ray jets in AGNs are commonly observed in FR II and FR I radio galaxies, but rarely in BL Lac objects, most probably due to their orientation close to the line of sight and the ensuing foreshortening effects. Only three BL Lac objects are known so far to contain a kpc-scale X-ray jet. In this paper we present the evidence for the existence of a fourth extended X-ray jet in the classical radio-selected source S5 2007+777, which for its hybrid FR I and FR II radio morphology has been classified as a HYMOR (HYbrid MOrphology Radio source). Our Chandra ACIS-S observations of this source revealed an X-ray counterpart to the 19'' long radio jet. Interestingly, the X-ray properties of the kpc-scale jet in S5 2007+777 are very similar to those observed in FR II jets. First, the X-ray morphology closely mirrors the radio one, with the X-rays being concentrated in the discrete radio knots. Second, the X-ray continuum of the jet/brightest knot is described by a very hard power law, with photon index ΓX ~ 1, although the uncertainties are large. Third, the optical upper limit from archival HST data implies a concave radio-to-X-ray SED. If the X-ray emission is attributed to IC/CMB with equipartition, strong beaming (δ = 13) is required, implying a very large scale (Mpc) jet. The beaming requirement can be somewhat relaxed assuming a magnetic field lower than equipartition. Alternatively, synchrotron emission from a second population of very high-energy electrons is viable. Comparison to other HYMOR jets detected with Chandra is discussed, as well as general implications for the origin of the FR I/FR II division.

Multiwavelength (Radio, X‐Ray, and γ‐Ray) Observations of the γ‐Ray Binary LS I +61 303

We present the results of the first multiwavelength observing campaign on the high-mass X-ray binary LS I +61 303 comprising observations at the TeV regime with the MAGIC telescope, along with X-ray observations with Chandra, and radio interferometric observations with the MERLIN, EVN and VLBA arrays, in October and November 2006. From our MERLIN observations, we can exclude the existence of large scale (~100 mas) persistent radio-jets. Our 5.0 GHz VLBA observations display morphological similarities to previous 8.4 GHz VLBA observations carried out at the same orbital phase, suggesting a high level of periodicity and stability of the processes behind the radio emission. This makes it unlikely that variability of the radio emission is due to the interaction of an outflow with variable wind clumps. If the radio emission is produced by a milliarcsecond scale jet, it should also show a stable, periodic behavior. It is then difficult to reconcile the absence of a large scale jet (~100 mas) in our observations with the evidence of a persistent relativistic jet reported previously. We find a possible hint of temporal correlation between the X-ray and TeV emissions and evidence for radio/TeV non-correlation, which points to the existence of one population of particles producing the radio emission and a different one producing the X-ray and TeV emissions. Finally, we present a quasi-simultaneous energy spectrum including radio, X-ray and TeV bands.

SSC SCENARIO FOR TEV EMISSION FROM NON-BLAZAR AGNs

M 87 is the first extragalactic source detected in the TeV γ-ray domain that is not a blazar, its large scale jet not being aligned to the line of sight. We present here a multi-blob synchrotron self-Compton model accounting explicitly for large viewing angles and moderate Lorentz factors as inferred from magnetohydrodynamic simulations of jet formation, motivated by the detection of M 87 at very high energies (VHE; E > 100 GeV ). Predictions are presented for the very high-energy emission of active galactic nuclei with extended optical or X-ray jet, which could be misaligned blazars but still show some moderate beaming. We include predictions for 3C 273, Cen A and PKS 0521–36.