A transition from parabolic to conical shape as a common effect in nearby AGN jets

Kovalev, Y. Y.; Pushkarev, A. B.; Nokhrina, E. E.; Plavin, A. V.; Бескин, В. С.; Chernoglazov, Alexander; Lister, M. L.; Savolainen, Tuomas

doi:10.1093/mnras/staa1121

Cited by 102 publications

(151 citation statements)

References 124 publications

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“…Assuming that the jet is confined by a spherical, hot accretion flow of the Bondi type (Bondi 1952), it was proposed that the transition, as well as the recollimation at HST-1 (e.g., Levinson & Globus 2017), may be induced by a change in the ambient pressure profile beyond r B . A transition from parabolic to conical expansion at similar distances (∼10 4 −10 6 R S ) was later observed in other sources, most recently in ten nearby objects in the MOJAVE 1 sample (Kovalev et al 2020), including both low-power (Fanaroff-Riley I, FRI) and high-power (Fanaroff-Riley II, FRII) radio galaxies, as well as BL Lacs.…”

Section: Introductionsupporting

confidence: 69%

“…By adopting a different approach and data set, Park et al (2020) have inferred that the shape transition in NGC 315 occurs at a distance of a few parsecs from the nucleus. On the other hand, Pushkarev et al (2017) and Kovalev et al (2020) performed an analysis of the 15 GHz VLBI stacked image, probing scales on the order of ∼1 to 10 de-projected parsecs, and obtained power-law indices k = 0.86 ± 0.01 and k = 1.07 ± 0.05, respectively, by fitting a single power-law. Kovalev et al (2020) also tested the presence of a transition along the 15 GHz jet, with negative results, and indeed the transition we detect is suggested to occur on smaller scales, unresolved at 15 GHz.…”

Section: Expansion Profilementioning

confidence: 99%

“…Such studies were mostly focused on the analysis of low-luminosity radio galaxies, such as NGC 6251 (Tseng et al 2016), 3C 84 (Giovannini et al 2018), 3C 270 (Nakahara et al 2018), 3C 264 (Boccardi et al 2019), NGC 1052 (Nakahara et al 2020) and M 87 (Asada & Nakamura 2012;Mertens et al 2016;Hada et al 2016;Kim et al 2018;Nokhrina et al 2019), but some constraints for high-luminosity radio galaxies, like Cygnus A (Boccardi et al 2016a,b;Nakahara et al 2019), and blazars (Giroletti et al 2008;Akiyama et al 2018;Hada et al 2018;Algaba et al 2019;Traianou et al 2020) were also provided. Moreover, part of the MOJAVE sample was investigated by Pushkarev et al (2017), Kovalev et al (2020). Asada & Nakamura (2012) have first shown that the inner jet in M 87 expands following a characteristic parabolic profile, and that this shape is preserved up to ∼10 5 Schwarzschild radii (R S ) from the black hole.…”

Section: Introductionmentioning

confidence: 99%

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Jet collimation in NGC 315 and other nearby AGN

Boccardi

Perucho

Casadio

et al. 2021

A&A

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Aims. The collimation of relativistic jets in galaxies is a poorly understood process. Detailed radio studies of the jet collimation region have been performed so far in a few individual objects, providing important constraints for jet formation models. However, the extent of the collimation zone as well as the nature of the external medium possibly confining the jet are still debated. Methods. In this article, we present a multifrequency and multiscale analysis of the radio galaxy NGC 315, including the use of mm-VLBI data up to 86 GHz, aimed at revealing the evolution of the jet collimation profile. We then consider results from the literature to compare the jet expansion profile in a sample of 27 low-redshift sources, mainly comprising radio galaxies and BL Lacs, which were classified based on the accretion properties as low-excitation (LEG) and high-excitation (HEG) galaxies. Results. We propose that the jet collimation in NGC 315 is completed on sub-parsec scales. A transition from a parabolic to conical jet shape is detected at zt = 0.58 ± 0.28 parsecs or ∼5 × 103 Schwarzschild radii (RS) from the central engine, a distance which is much smaller than the Bondi radius, rB ∼ 92 pc, estimated based on X-ray data. The jet in this and in a few other LEG in our sample may be initially confined by a thick disk extending out to ∼103 − 104RS. A comparison between the mass-scaled jet expansion profiles of all sources indicates that jets in HEG are surrounded by thicker disk-launched sheaths and collimate on larger scales with respect to jets in LEG. These results suggest that disk winds play an important role in the jet collimation mechanism, particularly in high-luminosity sources. The impact of winds on the origin of the FRI and FRII dichotomy in radio galaxies is also discussed.

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Section: Introductionsupporting

confidence: 69%

Section: Expansion Profilementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Jet collimation in NGC 315 and other nearby AGN

Boccardi

Perucho

Casadio

et al. 2021

A&A

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“…The model assumes a parabolic jet, as the observations suggest (Asada & Nakamura 2012;Kovalev et al 2020), with an acceleration zone near its base and constant flow beyond it. The parabolic shape of the jet implies that the radius of the jet as a function of distance from the black hole is given by R(z) = R 0 (z/z 0 ) 1/2 , where z 0 and R 0 denote the distance of the base of the jet from the black hole and the radius of the jet, respectively.…”

Section: Jet Modelmentioning

confidence: 99%

A quantitative explanation of the type-B QPOs in GX 339–4

Kylafis

Reig

Papadakis

2020

A&A

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Context. Type-B quasi periodic oscillations (QPOs) in black-hole X-ray binaries are a class of low-frequency QPOs that are observed in the soft intermediate state in the rising and the declining phases of an outburst. They are suspected to result from the precession of the jet that is ejected from the source. Aims. The objective of the present work is to investigate in detail the emissivity of the jet in hard X-rays and to see whether the type-B QPOs from GX 339−4, which is the best studied black-hole transient, can be explained quantitatively with a precessing jet. Methods. We used our simple jet model, which invokes Comptonization in the jet, and examined the angular dependence of the upscattered photons that emerge from the jet and their energy distribution, which is a power law. Results. Due to the elongation of the jet, assisted by the bulk motion of the electrons, the angular distribution of the emerging hard X-ray photons from the jet is not isotropic. More importantly, the photon-number spectral index, Γ, is an increasing function of the polar angle, θ, with respect to the axis of the jet. If the jet is fixed, then an observer at infinity sees the photon index, Γ, which corresponds to this specific observational direction. However, if the jet is precessing, then the observer sees a periodic variation of Γ with the precession period. Such a periodic variation of Γ has been observed in GX 339−4 and in this work, we reproduce it quantitatively, using our model. Conclusions. Our jet model nicely explains through quantitative means the type-B QPOs seen in GX 339−4 as originating from a precessing jet. The given model has previously explained several observed correlations thus far.

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“…When the proton reaching the light cylinder, the energy increases to

γ_{italicmax}^{((), 2 false/ 3)}

asymptotically shifted to the boundary of the light cylinder and then leaves it, passing into the jet region. The pre‐accelerated proton begins to increase its energy up to the maximum value

γ_{italicmax}^{((), 1)}

when it reaches the plane of intersection of the parabolic and conical jet profiles (Kovalev et al 2020). Upon reaching and crossing the jet boundary, the proton passes through the maximum potential difference, which gives the maximum energy.…”

Section: Particle Accelerationmentioning

confidence: 99%

Acceleration of the high‐energy protons in an active galactic nuclei

Istomin

Gunya

2021

Astron Nachr

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The process of stationary acceleration of protons by an electric field in the electromagnetic field of active galactic nuclei, including the regions of the magnetosphere of a supermassive black hole and a relativistic jet, is considered. The process of collisionless acceleration of the proton as a component of ultrahigh-energy cosmic rays is assumed. It is shown that during acceleration to the maximum energy max the main part of the energy is achieved by a proton in the magnetosphere up to (2∕3) max in the region of the light cylinder. Further achievement of the maximum energy max occurs in the jet region, where, depending on the parameters of the amplitudes of the electric and magnetic fields, various acceleration regimes are possible.

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A transition from parabolic to conical shape as a common effect in nearby AGN jets

Cited by 102 publications

References 124 publications

Jet collimation in NGC 315 and other nearby AGN

Jet collimation in NGC 315 and other nearby AGN

A quantitative explanation of the type-B QPOs in GX 339–4

Acceleration of the high‐energy protons in an active galactic nuclei

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