On the radio image of relativistic jets – I. Internal structure, Doppler boosting, and polarization maps

ABSTRACT In this first paper from forthcoming series of works devoted to radio image of relativistic jets from active galactic nuclei the role of internal structure of a flow is discussed. We determine the radial profiles of all physical values for reasonable Michel magnetization parameter σM and ambient pressure Pext. Maps of Doppler boosting factor δ and observed directions of linear polarization of synchrotron emission are also constructed.

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Magnetic inhibition of the recollimation instability in relativistic jets

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab828 ◽

2021 ◽

Vol 503 (4) ◽

pp. 4918-4929

Author(s):

Jin Matsumoto ◽

Serguei S Komissarov ◽

Konstantinos N Gourgouliatos

Keyword(s):

Magnetic Field ◽

Active Galactic Nuclei ◽

Three Dimensional ◽

Galactic Nuclei ◽

Rotating Fluids ◽

Relativistic Jets ◽

Azimuthal Magnetic Field ◽

Centrifugal Instability ◽

Magnetohydrodynamic Simulations

ABSTRACT In this paper, we describe the results of three-dimensional relativistic magnetohydrodynamic simulations aimed at probing the role of regular magnetic field on the development of the instability that accompanies recollimation of relativistic jets. In particular, we studied the recollimation driven by the reconfinement of jets from active galactic nuclei (AGN) by the thermal pressure of galactic coronas. We find that a relatively weak azimuthal magnetic field can completely suppress the recollimation instability in such jets, with the critical magnetization parameter σcr < 0.01. We argue that the recollimation instability is a variant of the centrifugal instability (CFI) and show that our results are consistent with the predictions based on the study of magnetic CFI in rotating fluids. The results are discussed in the context of AGN jets in general and the nature of the Fanaroff–Riley morphological division of extragalactic radio sources in particular.

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Parsec-Scale Synchrotron Emission from Hydrodynamic Relativistic Jets in Active Galactic Nuclei

The Astrophysical Journal ◽

10.1086/309623 ◽

1995 ◽

Vol 449 (1) ◽

Cited By ~ 79

Author(s):

J. L. Gómez, ◽

J. Ma. Martí, ◽

A. P. Marscher, ◽

J. Ma. Ibáñez, ◽

J. M. Marcaide

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Synchrotron Emission ◽

Relativistic Jets

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The Origin of Matter at the Base of Relativistic Jets in Active Galactic Nuclei

Universe ◽

10.3390/universe6070099 ◽

2020 ◽

Vol 6 (7) ◽

pp. 99

Author(s):

Gustavo Romero ◽

Eduardo Gutiérrez

Keyword(s):

Active Galactic Nuclei ◽

Gamma Rays ◽

Radio Galaxy ◽

Charged Particles ◽

Galactic Nuclei ◽

Complex Problem ◽

Synchrotron Emission ◽

Relativistic Jets ◽

Neutral Particles ◽

Very High

The generation of relativistic jets in active sources such as blazars is a complex problem with many aspects, most of them still not fully understood. Relativistic jets are likely produced by the accretion of matter and magnetic fields onto spinning black holes. Ergospheric dragging effects launch a Poynting-dominated outflow in the polar directions of these systems. Observations with very high resolution of the jet in the nearby radio galaxy M87 and evidence of extremely fast variability in the non-thermal radiation of several other objects indicate that charged particles produce synchrotron emission and gamma rays very close to the base of the jet. How these particles are injected into the magnetically shielded outflow is a mystery. Here we explore the effects of various processes in the hot accretion inflow close to the black hole that might result in the copious production of neutral particles which, through annihilation and decay in the jet’s funnel, might load the outflow with mass and charged particles on scales of a few Schwarzschild radii.

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Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽

10.3390/galaxies9020042 ◽

2021 ◽

Vol 9 (2) ◽

pp. 42

Author(s):

Claudia M. Raiteri ◽

Massimo Villata

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Plasma Jets ◽

Line Of Sight ◽

Optical Behaviour ◽

Relativistic Jets ◽

Comprehensive Picture ◽

Multi Wavelength ◽

Extreme Variability ◽

Continuous Range

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003476 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 375-375

Author(s):

Sarah White

Keyword(s):

Radio Emission ◽

Active Galactic Nuclei ◽

Visual Inspection ◽

Low Frequency ◽

Galactic Nuclei ◽

Radio Sources ◽

Relativistic Jets ◽

The Galaxy ◽

Murchison Widefield Array ◽

Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

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Understanding the origin of radio outflows in Seyfert galaxies using radio polarimetry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003014 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 247-251

Author(s):

Biny Sebastian ◽

Preeti Kharb ◽

Christopher P. O’ Dea ◽

Jack F. Gallimore ◽

Stefi A. Baum ◽

...

Keyword(s):

Magnetic Fields ◽

Radio Emission ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxy ◽

Seyfert Galaxies ◽

Starburst Galaxies ◽

Galactic Magnetic Fields ◽

5 Ghz

AbstractThe role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

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