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Journal articles on the topic 'AGN Jet'

Author: Grafiati

Published: 6 September 2023

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1

HOMAN, DANIEL C. "PHYSICAL PROPERTIES OF JETS IN AGN." International Journal of Modern Physics: Conference Series 08 (January 2012): 163–71. http://dx.doi.org/10.1142/s2010194512004552.

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I review constraints on the physical properties of AGN jets revealed through Very Long Baseline Interferometry (VLBI) studies of the structure and time-evolution of parsec-scale jets, including recent results from the MOJAVE program. In particular I focus on constraints available from very long time baseline studies which probe a wide range of jet behavior over many outbursts. Kinematic studies of propagating jet features find an apparent speed distribution that peaks around 10c for blazars, with speeds up to 50c observed. These observed speeds require Lorentz factors at least as large, implyi

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Sbarrato, Tullia, Paolo Padovani, and Gabriele Ghisellini. "The jet–disc connection in AGN." Proceedings of the International Astronomical Union 10, S313 (2014): 48–52. http://dx.doi.org/10.1017/s1743921315001854.

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AbstractWe present our latest results on the connection between the accretion rate and the power of relativistic jets. To this aim we use blazars, whose jet is pointing at us, with visible broad emission lines, along with broad lineless radio–galaxies. We trace the jet power with two proxies (gamma–ray and radio luminosities), while the broad emission lines are a direct measure of the accretion disc luminosity. We find a correlation between the broad emission line and the gamma–ray or luminosities in blazars, suggesting a direct tight connection between the jet and the accretion rate. Only ext

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Tanner, Ryan, and Kimberly A. Weaver. "Simulations of AGN-driven Galactic Outflow Morphology and Content." Astronomical Journal 163, no. 3 (2022): 134. http://dx.doi.org/10.3847/1538-3881/ac4d23.

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Abstract Using a series of 3D relativistic hydrodynamical simulations of active galactic nuclei (AGN) we investigate how AGN power, a clumpy interstellar medium (ISM) structure, and AGN jet angle with respect to the galactic disk affect the morphology and content of the resulting galactic outflow. For low-power AGN across three orders of magnitude of AGN luminosities (1041–1043 erg s−1) our simulations did not show significant changes to either the morphology or total mass of the outflow. Changing the angle of the AGN jet with respect to the galaxy did show small changes in the total outflow m

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King, Ashley L., Anne Lohfink, and Erin Kara. "AGN Coronae through a Jet Perspective." Astrophysical Journal 835, no. 2 (2017): 226. http://dx.doi.org/10.3847/1538-4357/835/2/226.

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Ferrari, Attilio. "Agn Jet Modeling: Setting the Stage." Astrophysics and Space Science 293, no. 1/2 (2004): 15–26. http://dx.doi.org/10.1023/b:astr.0000044648.48465.1a.

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Sbarrato, T., P. Padovani, and G. Ghisellini. "The jet–disc connection in AGN." Monthly Notices of the Royal Astronomical Society 445, no. 1 (2014): 81–92. http://dx.doi.org/10.1093/mnras/stu1759.

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Gurvits, Leonid I., Sándor Frey, and Zsolt Paragi. "Jets in AGN at extremely high redshifts." Proceedings of the International Astronomical Union 10, S313 (2014): 327–28. http://dx.doi.org/10.1017/s1743921315002434.

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The jet phenomenon is a trademark of active galactic nuclei (AGN). In most general terms, the current understanding of this phenomenon explains the jet appearance by effects of relativistic plasma physics. The fundamental source of energy that feeds the plasma flow is believed to be the gravitational field of a central supermassive black hole. While the mechanism of energy transfer and a multitude of effects controlling the plasma flow are yet to be understood, major properties of jets are strikingly similar in a broad range of scales from stellar to galactic. They are supposed to be controlle

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Komissarov, Serguei. "The remarkable AGN jets." Proceedings of the International Astronomical Union 12, S324 (2016): 141–48. http://dx.doi.org/10.1017/s1743921317001922.

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AbstractThe jets from active galactic nuclei exhibit stability which seems to be far superior compared to that of terrestrial and laboratory jets. They manage to propagate over distances up to a billion of initial jet radii. Yet this may not be an indication of some exotic physics but mainly a reflection of the specific environment these jets propagate through. The key property of this environment is a rapid decline of density and pressure along the jet, which promotes its rapid expansion. Such an expansion can suppress global instabilities, which require communication across the jet, and henc

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Kharb, Preeti, and Sasikumar Silpa. "Looking for Signatures of AGN Feedback in Radio-Quiet AGN." Galaxies 11, no. 1 (2023): 27. http://dx.doi.org/10.3390/galaxies11010027.

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In this article, we discuss the state of “AGN feedback” in radio-quiet (RQ) AGN. This study involves heterogeneous samples of nearby Seyfert and LINER galaxies as well as quasi-stellar objects (QSOs) that have been observed at low radio frequencies (few ∼100 MHz) with the upgraded Giant Meterwave Radio Telescope (GMRT) and ∼GHz frequencies with the Karl G. Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA). These multi-frequency, multi-resolution observations detect a range of arcsecond-scale radio spectral indices that are consistent with the presence of multiple contributors i

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Cielo, S., A. Babul, V. Antonuccio-Delogu, J. Silk, and M. Volonteri. "Feedback from reorienting AGN jets." Astronomy & Astrophysics 617 (September 2018): A58. http://dx.doi.org/10.1051/0004-6361/201832582.

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Aims. We test the effects of re-orienting jets from an active galactic nucleus (AGN) on the intracluster medium in a galaxy cluster environment with short central cooling time. We investigate both the appearance and the properties of the resulting cavities, and the efficiency of the jets in providing near-isotropic heating to the cooling cluster core. Methods. We use numerical simulations to explore four models of AGN jets over several active/inactive cycles. We keep the jet power and duration fixed across the models, varying only the jet re-orientation angle prescription. We track the total e

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Takahara, F. "High Energy Phenomena in AGN Jets." Symposium - International Astronomical Union 188 (1998): 153–56. http://dx.doi.org/10.1017/s0074180900114652.

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BL-Lac objects and optically violent variable quasars (OVVs), called together blazars, are characterized by rapid time variability, strong optical polarization, superluminal expansion and strong gamma-ray emission. Such properties are understood in the framework of a relativistic jet emanated from the central powerhouse. Blazars are considered to be objects for which the direction of the jet is very close to the line of sight.

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Coleman, Colin S. "Non-constant Superluminal Velocities in AGN." Publications of the Astronomical Society of Australia 8, no. 04 (1990): 353–56. http://dx.doi.org/10.1017/s1323358000023717.

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AbstractLarge apparent superluminal velocities are observed in nuclear jets in Active Galaxies, indicating the presence of relativistic velocities almost along the line of sight. If the flow is well collimated, as suggested by the large scale radio structure, the inferred alignment leads to difficulties with source statistics. Here a modification of the usual relativistic beam model is proposed, in which the jet is assumed to contain azimuthal (swirling) flow. Perturbation analysis is used to show that the jet is unstable to a Kelvin-Helmholtz helical standing wave, the wavelength of which inc

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Kovalev, Yuri. "The space VLBI mission RadioAstron: AGN results." Proceedings of the International Astronomical Union 15, S356 (2019): 256. http://dx.doi.org/10.1017/s1743921320003063.

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AbstractThe RadioAstron Space VLBI mission utilized the 10-m radio telescope on board the dedicated Spektr-R spacecraft to observe cosmic radio sources with an unprecedented angular resolution at centimeter wave lengths in total and polarized light. The longest baseline of the space-ground interferometer is about 350000 km. It operated in 2011–2019 together with 58 largest ground radio telescopes. Resolution as high as 10 microarcsec has been achieved. An overview of its AGN science results will be presented in the talk. It includes a probe of jet emission mechanism through brightness temperat

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Boccardi, B., M. Perucho, C. Casadio, et al. "Jet collimation in NGC 315 and other nearby AGN." Astronomy & Astrophysics 647 (March 2021): A67. http://dx.doi.org/10.1051/0004-6361/202039612.

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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

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Wardle, J. F. C. "Magnetic Fields in AGN." International Astronomical Union Colloquium 164 (1998): 97–103. http://dx.doi.org/10.1017/s0252921100044717.

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AbstractWe review VLBI polarization results. In particular, we discuss the a) “shock in jet paradigm”, b) the orientation of the magnetic field in jets as a function of optical identification, c) rotation measure and Faraday dispersion measurements as a probe of the narrow line region, and d) future directions of polarization observations. Results we emphasize are i) there is still a strong correlation between optical L/C ratio or EW and magnetic field orientation in the jets of blazars, even for high redshift weak-lined objects, ii) observed rotation measures are much smaller than expected fr

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Araudo, A. T., V. Bosch-Ramon, and G. E. Romero. "Radiation from matter entrainment in astrophysical jets: the AGN case." Proceedings of the International Astronomical Union 6, S275 (2010): 131–35. http://dx.doi.org/10.1017/s1743921310015802.

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AbstractJets are found in a variety of astrophysical sources. In all the cases the jet propagates with a supersonic velocity through the external medium, which can be inhomogeneous, and inhomogeneities could penetrate into the jet. The interaction of the jet material with an obstacle produces a bow-like shock within the jet in which particles can be accelerated up to relativistic energies and emit high-energy photons. In this work, we explore the active galactic nuclei scenario, focusing on the dynamical and radiative consequences of the interaction at different jet heights. We find that the p

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Mandal, Soham, Paul C. Duffell, and Yuan Li. "Numerical Investigation of Dynamical and Morphological Trends in Relativistic Jets." Astrophysical Journal 935, no. 1 (2022): 42. http://dx.doi.org/10.3847/1538-4357/ac7e42.

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Abstract Active galactic nuclei (AGN) show a range of morphologies and dynamical properties, which are determined not only by parameters intrinsic to the central engine but also their interaction with the surrounding environment. We investigate the connection of kiloparsec scale AGN jet properties to their intrinsic parameters and surroundings. This is done using a suite of 40 relativistic hydrodynamic simulations spanning a wide range of engine luminosities and opening angles. We explore AGN jet propagation with different ambient density profiles, including r −2 (self-similar solution) and r

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Meenakshi, Moun, Dipanjan Mukherjee, Alexander Y. Wagner, et al. "The extent of ionization in simulations of radio-loud AGNs impacting kpc gas discs." Monthly Notices of the Royal Astronomical Society 511, no. 2 (2022): 1622–36. http://dx.doi.org/10.1093/mnras/stac167.

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ABSTRACT We use the results of relativistic hydrodynamic simulations of jet-interstellar medium (ISM) interactions in a galaxy with a radio-loud AGN to quantify the extent of ionization in the central few kpcs of the gaseous galactic disc. We perform post-process radiative transfer of AGN radiation through the simulated gaseous jet-perturbed disc to estimate the extent of photo-ionization by the AGN with an incident luminosity of 1045 erg s−1. We also map the gas that is collisionally ionized due to shocks driven by the jet. The analysis was carried out for simulations with similar jet power (

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Mehdipour, Missagh, and Elisa Costantini. "Relation between winds and jets in radio-loud AGN." Astronomy & Astrophysics 625 (May 2019): A25. http://dx.doi.org/10.1051/0004-6361/201935205.

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We have investigated the relation between the two modes of outflow (wind and jet) in radio-loud active galactic nuclei (AGN). For this study we have carried out a systematic and homogeneous analysis of XMM-Newton spectra of a sample of 16 suitable radio-loud Seyfert-1 AGN. The ionised winds in these AGN are parameterised through high-resolution X-ray spectroscopy and photoionisation modelling. We discover a significant inverse correlation between the column density NH of the ionised wind and the radio-loudness parameter R of the jet. We explored different possible explanations for this NH-R re

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Lopez, Ericson D., and Susana Deustua. "AGN dusty plasma polarization features." Proceedings of the International Astronomical Union 10, S313 (2014): 352–57. http://dx.doi.org/10.1017/s1743921315002483.

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AbstractWe present the results of a theoretical study on the influence of dust particles on the polarization properties of the radiation that propagates along the jet in AGNs. First, a model for describing the interaction of dust particles, in addition to the electrons and ions, with electromagnetic radiation in a magneto-active plasma has been developed. From here, the contribution of dust particles to the Faraday rotation of the plane of polarization of the electric vector can be deduced. This model is evaluated for the outer region of the jet where the presence of dust particles are assumed

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Matveenko, L. I., and I. I. K. Pauliny-Toth. "The Injector and the AGN Core." International Astronomical Union Colloquium 164 (1998): 71–72. http://dx.doi.org/10.1017/s0252921100044584.

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Bååth, L. B. "AGN Variability and VLBI." Symposium - International Astronomical Union 159 (1994): 181–86. http://dx.doi.org/10.1017/s0074180900174996.

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This contribution discusses the connection between variability in radio and optical with structural variations observed with VLBI. Structural changes do not have to start in the core, and intensity variations may be caused by components in the jet outside the core. The scenario is probably more complicated than present day theories assume.

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Su, Kung-Yi, Philip F. Hopkins, Greg L. Bryan, et al. "Which AGN jets quench star formation in massive galaxies?" Monthly Notices of the Royal Astronomical Society 507, no. 1 (2021): 175–204. http://dx.doi.org/10.1093/mnras/stab2021.

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ABSTRACT Without additional heating, radiative cooling of the halo gas of massive galaxies (Milky Way-mass and above) produces cold gas or stars exceeding that observed. Heating from active galactic nucleus (AGN) jets is likely required, but the jet properties remain unclear. This is particularly challenging for galaxy simulations, where the resolution is orders-of-magnitude insufficient to resolve jet formation and evolution. On such scales, the uncertain parameters include the jet energy form [kinetic, thermal, cosmic ray (CR)]; energy, momentum, and mass flux; magnetic fields; opening angle

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Britzen, Silke, Michal Zajaček, Christian Fendt, et al. "Precession-induced Variability in AGN Jets and OJ 287." Astrophysical Journal 951, no. 2 (2023): 106. http://dx.doi.org/10.3847/1538-4357/accbbc.

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Abstract The combined study of the flaring of active galactic nuclei (AGNs) at radio wavelengths and parsec-scale jet kinematics with Very Long Baseline Interferometry has led to the view that (i) the observed flares are associated with ejections of synchrotron blobs from the core, and (ii) most of the flaring follows a one-to-one correlation with the ejection of the component. Recent results have added to the mounting evidence showing that the quasi-regular component injections into the relativistic jet may not be the only cause of the flux variability. We propose that AGN flux variability an

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Beall, J. H., John Guillory, D. V. Rose, Sabine Schindler, and S. Colafrancesco. "AGN Jet Interactions with the Intracluster Medium." Chinese Journal of Astronomy and Astrophysics 3, S1 (2003): 137–46. http://dx.doi.org/10.1088/1009-9271/3/s1/137.

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Antonuccio-Delogu, V., and J. Silk. "AGN feedback from jet-ISM/IGM interactions." Proceedings of the International Astronomical Union 3, S245 (2007): 31–32. http://dx.doi.org/10.1017/s1743921308017201.

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AbstractWe study the propagation of relativistic jets originating from AGNs within the Interstellar/Intergalactic Medium of their host galaxies, and use it to build a model for the inihibition of stellar formation within the expanding cocoon.

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van der Westhuizen, Izak P., Brian van Soelen, and Petrus J. Meintjes. "Emission modelling of hydrodynamic AGN jet simulations." Proceedings of the International Astronomical Union 14, S342 (2018): 209–13. http://dx.doi.org/10.1017/s1743921318008050.

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AbstractRadio-loud Active Galactic Nuclei (AGN) produce relativistic jets that can be modelled with relativistic hydrodynamic (RHD) simulations. In this study we present two such simulations of jets, used to investigate the parameters required to reproduce structures consistent with both FR I and FRII jets. In the first simulation a Lorentz factor of 10 and supersonic flow of Mach 30 were chosen, while for the second simulation a Lorentz factor of 1.0014 with a supersonic flow of Mach 4 was used. Over similar distances scales the first case shows a well collimated beam with a strong shock at t

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Torres-Albà, Núria, Valentí Bosch-Ramon, and Kazushi Iwasawa. "AGN jets versus accretion as reionization sources." Astronomy & Astrophysics 635 (March 2020): A57. http://dx.doi.org/10.1051/0004-6361/201936047.

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Context. Cosmic reionization put an end to the dark ages that came after the recombination era. Observations seem to favor the scenario of massive-star photons generated in low-mass galaxies being responsible for the bulk of reionization and, whereas a possible contribution from AGN accretion disks has been widely considered, they are currently thought to have had a minor role in reionization. Aims. We aim to study the possibility of AGN having contributed to reionization not only through their accretion disks, but also through ionizing photons coming from the AGN jets interacting with the int

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GABUZDA, D. C. "A FRAMEWORK FOR INTERPRETING OBSERVED PHENOMENA ASSOCIATED WITH RELATIVISTIC OUTFLOWS IN AGN." International Journal of Modern Physics D 17, no. 09 (2008): 1521–30. http://dx.doi.org/10.1142/s0218271808013108.

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A growing number of jets in active galactic nuclei (AGN) show clear signs of helical magnetic (B) fields: Faraday-rotation gradients across the VLBI jets, extended regions of jet with orthogonal B fields, transverse polarization and total-intensity structures characteristic of helical fields, interknot polarization implying underlying orthogonal B fields, and a predominance of orthogonal B fields in the VLBI cores. In addition, a link has now been found between the circular polarization detected in AGN cores and the presence of helical jet B fields within these cores. This now abundant evidenc

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Chatterjee, K., M. Liska, A. Tchekhovskoy, and S. B. Markoff. "Accelerating AGN jets to parsec scales using general relativistic MHD simulations." Monthly Notices of the Royal Astronomical Society 490, no. 2 (2019): 2200–2218. http://dx.doi.org/10.1093/mnras/stz2626.

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ABSTRACT Accreting black holes produce collimated outflows, or jets, that traverse many orders of magnitude in distance, accelerate to relativistic velocities, and collimate into tight opening angles. Of these, perhaps the least understood is jet collimation due to the interaction with the ambient medium. In order to investigate this interaction, we carried out axisymmetric general relativistic magnetohydrodynamic simulations of jets produced by a large accretion disc, spanning over 5 orders of magnitude in time and distance, at an unprecedented resolution. Supported by such a disc, the jet at

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Krichbaum, T. P., W. Alef, and A. Witzel. "The Sub-Parsec Scale Jets of AGN." Symposium - International Astronomical Union 175 (1996): 11–13. http://dx.doi.org/10.1017/s007418090007981x.

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With an angular resolutions of 0.05–0.2 mas, millimeter-VLBI1 observations (at 22, 43, and 86 GHz) allow to investigate the very central –sub-parsec scale – regions of active galactic nuclei (AGN), which are self-absorbed at lower frequencies. Here we briefly present preliminary results from recent observations of Cygnus A at 22 & 43 GHz, which reveal evidence for subluminal motion in jet and counter-jet, and 86 GHz VLBI observations of two extreme γ – blazars, suggesting a tight correlation between their γ – ray activity and the generation of jets.

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Chu, Han-Shu, L. B. Baath, Fu-Jun Zhang, and R. E. Spencer. "Discovery of Helical Magnetic Fields in AGN, and CME and Ejection of Large-Scale Magnetic Fields from AGN." Symposium - International Astronomical Union 214 (2003): 303–8. http://dx.doi.org/10.1017/s007418090019463x.

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Magnetic Fields are the crucial and most important ingredient involved in the processes of various violent activities in Active Galactic Nuclei and other celestial bodies. The generally accepted 2-sided symmetric-jets model of active galactic nuclei (AGN) does not include the magnetic fields. We present here the first direct detection of helical magnetic field in AGN, and the first direct detection of ejection of large scale magnetic fields from AGN. (CME) 2. The annular (helical) magnetic field is responsible for the collimation of the jet (through Pinch Effect) and may be of crucial importan

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Ekejiuba, Ifeanyi E. "Radiative Signatures of Neutron Beams in AGN." Symposium - International Astronomical Union 159 (1994): 345. http://dx.doi.org/10.1017/s0074180900175461.

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The escape of relativistic neutrons from their production region can have various consequencies for the morphology of active galaxies. The phenomena of luminosity gaps and radio jet lighting in extragalactic radio sources (EGRSs) fit into the model that employs relativistic neutrons as the vector for particle and energy transport out of the central engines of AGNs. The central radio gaps reveal themselves as regions of relativistic neutron beam transport. The relativistic neutrons, which decay in flight after traveling for ∼ 103 γn s, produce secondaries which are responsible for the radio jet

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ALGABA, JUAN C. "PROBING HELICAL MAGNETIC FIELDS IN AGN BY ROTATION MEASURE GRADIENTS STUDIES." International Journal of Modern Physics: Conference Series 08 (January 2012): 303–6. http://dx.doi.org/10.1142/s2010194512004758.

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One of the tools that can provide evidence about the existence of helical magnetic fields in AGN is the observation of rotation measure gradients across the jet. Such observations have been previously made successfully, proving that such gradients are far from being rare, but common and typically persistent over several years, although some of them may show a reversal in the direction along the jet. Further studies of rotation measure gradients can help us in our understanding of the magnetic field properties and structure in the base of the jets. We studied Very Long Baseline Array (VLBA) pol

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BIBI, F. ALOUANI, and J. BINNEY. "AGN JET AND THERMAL CONDUCTION IN COOLING FLOW CLUSTERS." International Journal of Modern Physics D 17, no. 10 (2008): 1953–59. http://dx.doi.org/10.1142/s0218271808013625.

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We consider the effect of thermal conduction along with AGN jet feedback on the intracluster medium (ICM) in cooling flow clusters. A series of three-dimensional AMR hydrodynamic simulations has been carried out to analyze the dynamic of such interaction. We show the limit of applicability of the Spitzer thermal conduction during jet/ICM interaction.

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Gabuzda, Denise C., Matt Nagle, and Naomi Roche. "The jets of AGN as giant coaxial cables." Astronomy & Astrophysics 612 (April 2018): A67. http://dx.doi.org/10.1051/0004-6361/201732136.

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Context. The currents carried by the jets of active galactic nuclei (AGNs) can be probed using maps of the Faraday rotation measure (RM), since a jet current will be accompanied by a toroidal magnetic field, which will give rise to a systematic change in the RM across the jet. Aims. The aim of this study is to identify new AGNs displaying statistically significant transverse RM gradients across their parsec-scale jets, in order to determine how often helical magnetic fields occur in AGN jets, and to look for overall patterns in the implied directions for the toroidal field components and jet c

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Britzen, S., R. C. Vermeulen, G. B. Taylor, et al. "CJ-F: The Kinematics of 241 AGN." Symposium - International Astronomical Union 205 (2001): 106–9. http://dx.doi.org/10.1017/s0074180900220615.

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We present first results from the analysis of multi-epoch VLBI observations of 241 sources in the CJ-F sample (Caltech Jodrell-Flat-spectrum, Taylor et al. 1996). We have been obtaining 5 GHz VLBI (global and VLBA) snapshot observations of the CJ-F sources (complete with 293 sources) since 1990 in order to create a valid database for thorough statistical tests of pc-scale jet motion in AGN. All 241 CJ-F AGN have been observed at least three times with the VLBA, which enables us to investigate jet component motions and paths. In particular, we concentrate on the analysis of those properties sup

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Pötzl, F. M., A. P. Lobanov, E. Ros, et al. "Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron." Astronomy & Astrophysics 648 (April 2021): A82. http://dx.doi.org/10.1051/0004-6361/202039493.

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Context. Supermassive black holes in the centres of radio-loud active galactic nuclei (AGN) can produce collimated relativistic outflows (jets). Magnetic fields are thought to play a key role in the formation and collimation of these jets, but the details are much debated. Aims. We study the innermost jet morphology and magnetic field strength in the AGN 3C 345 with an unprecedented resolution using images obtained within the framework of the key science programme on AGN polarisation of the Space VLBI mission RadioAstron. Methods. We observed the flat spectrum radio quasar 3C 345 at 1.6 GHz on

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Lister, M. L., D. C. Homan, K. I. Kellermann, et al. "Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments. XVIII. Kinematics and Inner Jet Evolution of Bright Radio-loud Active Galaxies." Astrophysical Journal 923, no. 1 (2021): 30. http://dx.doi.org/10.3847/1538-4357/ac230f.

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Abstract We have analyzed the parsec-scale jet kinematics of 447 bright radio-loud active active galactic nuclei (AGN), based on 15 GHz Very Long Baseline Array (VLBA) data obtained between 1994 August 31 and 2019 August 4. We present new total intensity and linear polarization maps obtained between 2017 January 1 and 2019 August 4 for 143 of these AGN. We tracked 1923 bright features for five or more epochs in 419 jets. The majority (60%) of the well-sampled jet features show either accelerated or nonradial motion. In 47 jets there is at least one nonaccelerating feature with an unusually slo

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O'SULLIVAN, S. P., and D. C. GABUZDA. "PARSEC-SCALE INVESTIGATION OF THE MAGNETIC FIELD STRUCTURE OF SEVERAL AGN JETS." International Journal of Modern Physics D 17, no. 09 (2008): 1553–60. http://dx.doi.org/10.1142/s0218271808013145.

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Multi-frequency (4.6, 5, 5.5, 8, 8.8, 13, 15, 22 & 43 GHz) polarization observations of six "blazars" were obtained on the American Very Long Baseline Array (VLBA) over a 24-hr period on 2 July 2006. Observing at several frequencies, separated by short and long intervals, enabled reliable determination of the distribution of Faraday rotation on a range of scales. In all cases the magnitude of the RM increases in the higher frequency observations, implying that the electron density and/or magnetic field strength is increasing as we get closer to the central engine. After correcting for Fara

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Okino, Hiroki, Kazunori Akiyama, Keiichi Asada, et al. "Collimation of the Relativistic Jet in the Quasar 3C 273." Astrophysical Journal 940, no. 1 (2022): 65. http://dx.doi.org/10.3847/1538-4357/ac97e5.

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Abstract The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGNs) is one of the key questions to understand the nature of AGN jets. However, little is known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar 3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama Large Millimeter/submil

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Guo, Fulai. "The AGN Jet Model of the Fermi Bubbles." Proceedings of the International Astronomical Union 11, S322 (2016): 189–92. http://dx.doi.org/10.1017/s1743921316012023.

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AbstractThe nature and origin of the Fermi bubbles detected in the inner Galaxy remain elusive. In this paper, we briefly discuss some recent theoretical and observational developments, with a focus on the AGN jet model. Analogous to radio lobes observed in massive galaxies, the Fermi bubbles could be naturally produced by a pair of opposing jets emanating nearly along the Galaxy’s rotation axis from the Galactic center. Our two-fluid hydrodynamic simulations reproduce quite well the bubble location and shape, and interface instabilities at the bubble surface could be effectively suppressed by

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Jolley, E. J. D., and Z. Kuncic. "Jet-driven disk accretion in low luminosity AGN?" Astrophysics and Space Science 310, no. 3-4 (2007): 327–32. http://dx.doi.org/10.1007/s10509-007-9543-3.

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Jolley, E. J. D., and Z. Kuncic. "Jet-driven disk accretion in low luminosity AGN?*." Astrophysics and Space Science 311, no. 1-3 (2007): 257–62. http://dx.doi.org/10.1007/s10509-007-9653-y.

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Yuan, F., S. Markoff, H. Falcke, and P. L. Biermann. "NGC 4258: A jet-dominated low-luminosity AGN?" Astronomy & Astrophysics 391, no. 1 (2002): 139–48. http://dx.doi.org/10.1051/0004-6361:20020817.

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Dugan, Zachary, Sarah Bryan, Volker Gaibler, Joseph Silk, and Marcel Haas. "STELLAR SIGNATURES OF AGN-JET-TRIGGERED STAR FORMATION." Astrophysical Journal 796, no. 2 (2014): 113. http://dx.doi.org/10.1088/0004-637x/796/2/113.

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Rokak, E. "Accretion Disks and Line Emission in AGN." International Astronomical Union Colloquium 159 (1997): 56–63. http://dx.doi.org/10.1017/s0252921100039634.

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AbstractIrradiated accretion disks around massive black holes are expected to produce part of the line spectrum of AGN, but most of the disk emission must be thermal, observed at UV wavelengths. The two emission components, lines and continuum, are fitted by a unique accretion-disk model that gives the mass of the black hole and the inclination of the disk. The distribution of the disk inclination in a complete sample of Seyfert 1 galaxies suggests that their nuclei are orientation-selected, affected by strong absorption at low disk latitudes. The black-hole masses in the same sample confirm t

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Kutkin, A. M., I. N. Pashchenko, K. V. Sokolovsky, Y. Y. Kovalev, M. F. Aller, and H. D. Aller. "Opacity, variability, and kinematics of AGN jets." Monthly Notices of the Royal Astronomical Society 486, no. 1 (2019): 430–39. http://dx.doi.org/10.1093/mnras/stz885.

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ABSTRACT Synchrotron self-absorption in active galactic nuclei (AGN) jets manifests itself as a time delay between flares observed at high and low radio frequencies. It is also responsible for the observing frequency-dependent change in size and position of the apparent base of the jet, aka the core shift effect, detected with very long baseline interferometry (VLBI). We measure the time delays and the core shifts in 11 radio-loud AGN to estimate the speed of their jets without relying on multi-epoch VLBI kinematics analysis. The 15–8 GHz total flux density time lags are obtained using Gaussia

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Combes, Francoise. "Circum-nuclear molecular disks: Role in AGN fueling and feedback." Proceedings of the International Astronomical Union 15, S359 (2020): 312–17. http://dx.doi.org/10.1017/s1743921320001544.

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AbstractGas fueling AGN (Active Galaxy Nuclei) is now traceable at high-resolution with ALMA (Atacama Large Millimeter Array) and NOEMA (NOrthern Extended Millimeter Array). Dynamical mechanisms are essential to exchange angular momentum and drive the gas to the super-massive black hole. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching 10pc scale (50mas), may bring smoking gun evidence of fueling, within a randomly oriented nuclear gas disk. AGN feedback is also observed, in the form of narrow and collimated molecular outflows, which point towar

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Chu, H. S., F. J. Zhang, and R. E. Spencer. "CME and Ejection of Large Scale Magnetic Fields, Helical Magnetic Fields, and Intrinsically Asymmetric Jets - New Findings in AGN." International Astronomical Union Colloquium 164 (1998): 121–22. http://dx.doi.org/10.1017/s0252921100044808.

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AbstractThe orthodox model of active galactic nuclei (AGN), as is generally accepted, is that of Rees. We have found an AGN (3C 147) which has a counter-jet much longer than the main jet. It also has an unusual sideways ejection from the nuclear region. Both of these and the 3-jet structure per se do not seem to conform with the general accepted model, and are also not explained by relativistic beaming effects. We speculate that this is due to coronal mass ejection (CME) in the accretion disk corona. Recently, we have found convincing new evidence that this is true. We have also found direct e

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