scholarly journals The Effect of Nonaxisymmetric Radiative Drag on Relativistic Jets in Active Galactic Nuclei

2001 ◽  
Vol 18 (3) ◽  
pp. 215-220
Author(s):  
Qinghuan Luo
Keyword(s):  
Black Hole ◽  
Electromagnetic Radiation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radiation Force ◽  
Asymmetric Distribution ◽  
Relativistic Jets ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Axially Asymmetric

AbstractThe effect of nonaxisymmetric radiation drag on relativistic jets in active galactic nuclei (AGN) is discussed. The radiation force due to inverse Compton scattering of photon fields from a noncircular accretion disk is calculated. It is shown that such nonaxisymmetric drag can cause jet path distortion within the subparsec region of the black hole. This subparsec scale distortion is potentially observable with the current VLBI, VLBA techniques. Any modulation of the axially asymmetric distribution of disk emission can result in variability in electromagnetic radiation from the jet.

scholarly journals The role of AGN jets in the reionization epoch

2018 ◽  
Vol 617 ◽  
pp. L3 ◽  
Author(s):  
V. Bosch-Ramon
Keyword(s):  
Black Hole ◽  
Ionizing Radiation ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Black Hole Mass ◽  
Star Forming ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Mass Functions ◽  
The Universe

The reionization of the Universe ends the dark ages that started after the recombination era. In the case of H, reionization finishes around z ~ 6. Faint star-forming galaxies are the best candidate sources of the H-ionizing radiation, although active galactic nuclei may have also contributed. We have explored whether the termination regions of the jets from active galactic nuclei may have contributed significantly to the ionization of H in the late reionization epoch, around z ~ 6−7. We assumed that, as it has been proposed, active galactic nuclei at z ~ 6 may have presented a high jet fraction, accretion rate, and duty cycle, and that non-thermal electrons contribute significantly to the pressure of jet termination regions. Empirical black-hole mass functions were adopted to characterize the population of active galactic nuclei. From all this, estimates were derived for the isotropic H-ionizing radiation produced in the jet termination regions, at z ~ 6, through inverse Compton scattering off CMB photons. We find that the termination regions of the jets of active galactic nuclei may have radiated most of their energy in the form of H-ionizing radiation at z ~ 6. For typical black-hole mass functions at that redshift, under the considered conditions (long-lasting, common, and very active galactic nuclei with jets), the contribution of these jets to maintain (and possibly enhance) the ionization of H may have been non-negligible. We conclude that the termination regions of jets from active galactic nuclei could have had a significant role in the reionization of the Universe at z ≳ 6.

scholarly journals Observational View of Magnetic Fields in Active Galactic Nuclei Jets

2016 ◽  
Vol 12 (S324) ◽  
pp. 149-156
Author(s):  
Talvikki Hovatta
Keyword(s):  
Black Hole ◽  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Short Review ◽  
Relativistic Jets ◽  
The Past ◽  
Emission Models ◽  
Active Galactic Nuclei Jets ◽  
The Magnetic Field

AbstractAccording to the currently favored picture, relativistic jets in active galactic nuclei (AGN) are launched in the vicinity of the black hole by magnetic fields extracting energy from the spinning black hole or the accretion disk. In the past decades, various models from shocks to magnetic reconnection have been proposed as the energy dissipation mechanism in the jets. This paper presents a short review on how linear polarization observations can be used to constrain the magnetic field structure in the jets of AGN, and how the observations can be used to constrain the various emission models.

scholarly journals Anisotropic Effects in Thomson Cascade Models of Active Galactic Nuclei

1994 ◽  
Vol 159 ◽  
pp. 343-343
Author(s):  
Matthew G. Baring
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Spectral Indices ◽  
Scattering Mechanism ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Cascade Models ◽  
Γ Rays ◽  
Viewing Perspective

CGRO observations of high energy γ-rays from active galactic nuclei (AGN) suggest that beaming may be prevalent in these sources. Anisotropic effects in AGN continuum spectra produced by the inverse Compton scattering mechanism are outlined, in particular the resulting spectral breaks and modification of spectral indices that depend strongly on the electron anisotropy and the observational viewing perspective.

scholarly journals The Effect of Radiation Drag on Relativistic Bulk Flows in Active Galactic Nuclei

2002 ◽  
Vol 19 (1) ◽  
pp. 122-124
Author(s):  
Qinghuan Luo
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Broad Line ◽  
Nuclear Region ◽  
Inverse Compton Scattering ◽  
Broad Line Region ◽  
Line Region ◽  
Inverse Compton ◽  
Γ Ray ◽  
Dusty Torus

AbstractThe effect of radiation drag on relativistic bulk flows is re-examined. Highly relativistic bulk flows in the nuclear region are subject to Compton drag, i.e. radiation deceleration as a result of inverse Compton scattering of ambient soft photon fields from emission from the accretion disk, broad line region, or dusty torus. Possible observational consequences of X-/γ-ray emission produced from Compton drag are specifically discussed.

scholarly journals Symmetry Breaking in Dynamical Encounters in the Disks of Active Galactic Nuclei

2021 ◽  
Vol 923 (2) ◽  
pp. L23
Author(s):  
Yi-Han Wang ◽  
Barry McKernan ◽  
Saavik Ford ◽  
Rosalba Perna ◽  
Nathan W. C. Leigh ◽  
...  
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Active Galactic Nuclei ◽  
Numerical Experiments ◽  
Semimajor Axis ◽  
Galactic Nuclei ◽  
High Accuracy ◽  
Broken Symmetry ◽  
Asymmetric Distribution ◽  
Binary Black Hole

Abstract The disks of active galactic nuclei (AGNs) may be important sites of binary black hole (BBH) mergers. Here we show via numerical experiments with the high-accuracy, high-precision code SpaceHub that broken symmetry in dynamical encounters in AGN disks can lead to asymmetry between prograde and retrograde BBH mergers. The direction of the hardening asymmetry depends on the initial binary semimajor axis. Under the assumption that the spin of the BHs becomes aligned with the angular momentum of the disk on a short timescale compared with the encounter timescale, an asymmetric distribution of mass-weighted projected spin χ eff is predicted in LIGO–Virgo detections of BBH mergers from AGN disks. In particular, this model predicts that positive χ eff BBH mergers are most likely for encounters with massive tertiaries in migration traps at radial distances ≳500–600 gravitational radii.

scholarly journals Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽  
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.

scholarly journals Epicyclic Oscillations around Simpson–Visser Regular Black Holes and Wormholes

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 279
Author(s):  
Zdeněk Stuchlík ◽  
Jaroslav Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Observational Data ◽  
High Frequency ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Periodic Oscillations ◽  
High Length ◽  
Circular Geodesic

We study epicyclic oscillatory motion along circular geodesics of the Simpson–Visser meta-geometry describing in a unique way regular black-bounce black holes and reflection-symmetric wormholes by using a length parameter l. We give the frequencies of the orbital and epicyclic motion in a Keplerian disc with inner edge at the innermost circular geodesic located above the black hole outer horizon or on the our side of the wormhole. We use these frequencies in the epicyclic resonance version of the so-called geodesic models of high-frequency quasi-periodic oscillations (HF QPOs) observed in microquasars and around supermassive black holes in active galactic nuclei to test the ability of this meta-geometry to improve the fitting of HF QPOs observational data from the surrounding of supermassive black holes. We demonstrate that this is really possible for wormholes with sufficiently high length parameter l.

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

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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