Relativistic AGN jets III. Synthesis of synchrotron emission from Double-Double Radio Galaxies

Abstract

The class of Double-Double Radio Galaxies (DDRGs) relates to episodic jet outbursts. How various regions and components add to the total intensity in radio images is less well known. In this paper we synthesize synchrotron images for DDRGs based on special relativistic hydrodynamic simulations, making advanced approximations for the magnetic fields. We study the synchrotron images for: Three different radial jet profiles; Ordered, entangled or mixed magnetic fields; Spectral ageing from synchrotron cooling; The contribution from different jet components; The viewing angle and Doppler (de-)boosting; The various epochs of the evolution of the DDRG. To link our results to observational data, we adopt to J1835+6204 as a reference source. In all cases the synthesized synchrotron images show two clear pairs of hotspots, in the inner and outer lobes. The best resemblance is obtained for the piecewise isochoric jet model, for a viewing angle of approximately $\vartheta \sim -71^{\circ }$, i.e. inclined with the lower jet towards the observer, with predominantly entangled ($\gtrsim 70$ per cent of the magnetic pressure) in turbulent, rather than ordered fields. The effects of spectral ageing become significant when the ratio of observation frequencies and cut-off frequency ${\nu }_{\mathrm{obs}}/{\nu }_{\infty ,0}\gtrsim 10^{-3}$, corresponding to $\sim 3\cdot 10^2$ MHz. For viewing angles $\vartheta \lesssim -30^{\circ }$, a DDRG morphology can no longer be recognized. The second jets must be injected within $\lesssim$ 4 per cent of the lifetime of the first jets for a DDRG structure to emerge, which is relevant for Active Galactic Nuclei feedback constraints.

24 pages, 8 figures

References in corpus (18)

• Stability of Relativistic Jets from Rotating, Accreting Black Holes via Fully Three-Dimensional Magnetohydrodynamic Simulations
• MPI-AMRVAC for Solar and Astrophysics
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• Simulated synchrotron emission from Pulsar Wind Nebulae
• The Energetics and Lifetimes of Local Radio Active Galactic Nuclei
• Intrinsic Brightness Temperatures of AGN Jets
• Kinematics of the M87 jet in the collimation zone: gradual acceleration and velocity stratification
• Extragalactic jets with helical magnetic fields: relativistic MHD simulations
• The Lifetime of FRIIs in Groups and Clusters: Implications for Radio-Mode Feedback
• Transverse Faraday-Rotation Gradients Across the Jets of 15 Active Galactic Nuclei
• Optical and radio properties of extragalactic radio sources with recurrent jet activity
• Doppler Boosting, Superluminal Motion, and the Kinematics of AGN Jets
• Modelling MHD accretion-ejection - episodic ejections of jets triggered by a mean-field disk dynamo
• PKS B1545-321: Bow shocks of a relativistic jet?
• Investigating the spectral age problem with powerful radio galaxies
• A low-frequency study of recently identified double-double radio galaxies
• Multifrequency study of a double-double radio galaxy J1706+4340
• Observational signatures of magnetic field structure in relativistic AGN jets

Cited by in corpus (2)

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