Emission modelling of hydrodynamic AGN jet simulations

2018 ◽  
Vol 14 (S342) ◽  
pp. 209-213
Author(s):  
Izak P. van der Westhuizen ◽  
Brian van Soelen ◽  
Petrus J. Meintjes
Keyword(s):  
Supersonic Flow ◽  
Active Galactic Nuclei ◽  
Ambient Medium ◽  
Strong Shock ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Single Frequency ◽  
First Case ◽  
Emission Modelling ◽  
Collimated Beam

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 the interface between the jet and ambient medium while the second case shows a less stable beam and a larger cocoon. To determine whether the simulated physical structures are consistent with the observed FR I/II jets, the synchrotron emission has been calculated to produce radio maps at a single frequency of 1.5 GHz.

scholarly journals Statistical Effects of Doppler Beaming and Malmquist Bias on Flux-Limited Samples of Compact Radio Sources

1998 ◽  
Vol 164 ◽  
pp. 137-138
Author(s):  
Matthew L. Lister ◽  
Alan P. Marscher
Keyword(s):  
Active Galactic Nuclei ◽  
Luminosity Function ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Radio Sources ◽  
Apparent Velocity ◽  
Parent Population ◽  
Relativistic Jet ◽  
Spectrum Radio ◽  
Statistical Effects

AbstractWe examine the effects of Doppler beaming on flux-limited samples of compact extragalactic radio sources using Monte Carlo simulations. We incorporate a luminosity function and z-distribution for the parent population, and investigate models in which the unbeamed synchrotron luminosity L of a relativistic jet is related to its bulk Lorentz factor Γ. The predicted flux density, redshift, monochromatic luminosity, and apparent velocity distributions of our simulated flux-limited samples are compared to the Caltech-Jodrell Bank (CJF) sample of flat-spectrum, radio core-dominated active galactic nuclei (AGNs).We find that a relation between L and Γ is not needed to reproduce the characteristics of the CJF sample. Introducing a positive correlation between these quantities results in an underabundance of objects with high viewing angles, while a negative correlation gives generally poor fits to the data.

scholarly journals Accelerating AGN jets to parsec scales using general relativistic MHD simulations

2019 ◽  
Vol 490 (2) ◽  
pp. 2200-2218 ◽  
Author(s):  
K Chatterjee ◽  
M Liska ◽  
A Tchekhovskoy ◽  
S B Markoff
Keyword(s):  
Ambient Medium ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Opening Angle ◽  
Long Baseline ◽  
General Relativistic ◽  
Field Lines ◽  
Magnetohydrodynamic Simulations ◽  
Jet Collimation ◽  
Sheath Structure

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 attains a parabolic shape, similar to the M87 galaxy jet, and the product of the Lorentz factor and the jet half-opening angle, γθ ≪ 1, similar to values found from very long baseline interferometry (VLBI) observations of active galactic nuclei (AGNs) jets; this suggests extended discs in AGNs. We find that the interaction between the jet and the ambient medium leads to the development of pinch instabilities, which produce significant radial and lateral variability across the jet by converting magnetic and kinetic energy into heat. Thus pinched regions in the jet can be detectable as radiating hotspots and may provide an ideal site for particle acceleration. Pinching also causes gas from the ambient medium to become squeezed between magnetic field lines in the jet, leading to enhanced mass loading and deceleration of the jet to non-relativistic speeds, potentially contributing to the spine-sheath structure observed in AGN outflows.

scholarly journals General Relativistic Simulation of Jet Formation from Magnetized Accretion Disk

1997 ◽  
Vol 163 ◽  
pp. 667-671
Author(s):  
Shinji Koide ◽  
Kazunari Shibata ◽  
Takahiro Kudoh
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Numerical Code ◽  
Jet Formation ◽  
Relativistic Jet ◽  
Relativistic Regime ◽  
General Relativistic

AbstractRecently, superluminal motions are observed not only from active galactic nuclei but also in our Galaxy. These phenomena are explained as relativistic jets propagating almost toward us with Lorentz factor more than 2. For the formation of such a relativistic jet, magnetically driven mechanism around a black hole is most promising. We have extended the 2.5D Newtonian MHD jet model (Shibata & Uchida 1986) to general relativistic regime. For this purpose, we have developed a general relativistic magnetohydrodynamic (GRMHD) numerical code and applied it to the simulation of the magnetized accretion disk around a black hole. We have found the formation of magnetically driven jets with 86 percent of light velocity (i.e. Lorentz factor ~ 2.0).

scholarly journals BL LAC POPULATION STUDY AT HIGH ENERGIES

2014 ◽  
Vol 28 ◽  
pp. 1460177
Author(s):  
LUCIE GÉRARD ◽  
GILLES HENRI ◽  
SANTIAGO PITA ◽  
MICHAEL PUNCH
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Opening Angle ◽  
Parent Population ◽  
High Energies ◽  
Relativistic Jet ◽  
Radiative Model ◽  
Doppler Factor ◽  
Bl Lacs

In the framework of Active Galactic Nuclei (AGN) unification, BL Lacs and their parent population would share the same intrinsic characteristics, the observational differences being due to the orientation of the relativistic jet compared to the line of sight. BL Lacs would be the objects whose jet is oriented towards us, their emission being amplified by the relativistic Doppler boosting. Constraints arising from fast variability and/or large optical depth to pair production commonly imply large Lorentz factors. The growing number of BL Lacs detected at HE (> 100 MeV) and VHE (> 100 GeV) is a challenge for this unification scheme. Indeed, the high values of Doppler factor needed in the simplest radiative model to explain the emission of these sources imply a large density for the parent population. A possible solution to this Doppler factor crisis lies in considering different geometries for the jet. In this study, we use the BL Lacs detected at HE and VHE to investigate the intrinsic properties of the associated parent population. Using the results presented in Fermi's second AGN catalog and performing MC simulations of the parent population, we constrain the jet parameters: its intrinsic luminosity, Lorentz factor and geometric opening angle. The simulated density of parent population and Doppler factors of the objects detectable at HE within this population are presented according to the jet parameters.

scholarly journals Physical Processes in Active Galactic Nuclei

1986 ◽  
Vol 89 ◽  
pp. 324-345
Author(s):  
Roland Svensson
Keyword(s):  
Pair Production ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Rest Mass ◽  
Galactic Nuclei ◽  
Nonthermal Plasma ◽  
Lorentz Factor ◽  
Analytical Models ◽  
Potential Wells ◽  
Electron Positron

AbstractActive galactic nuclei (AGNs) emit continuum radiation evenly spread over up to ten decades in frequency from the radio into the gamma-ray range. Plausible emission mechanisms and their characteristics are reviewed. In the deep potential wells around black holes the mean energy per proton can reach 100 MeV. Part or all of this energy may be channeled to all electrons equally (thermal plasma) or, preferentially, into only a small fraction of the electrons (nonthermal plasma). In the former case thermal Comptonization of soft photons may be the dominant emission mechanism, while in the latter case the synchrotron and the inverse Compton scattering process (synchro-self-Compton) are likely to dominate.When the compactness parameter L (hν≈mc2 )/R. (power L, radius R) exceeds about 1030 ergs cm−1s−1 or L>Lc ≡ 1030R ergs s−1, then electron-positron pair production takes place due to photon-photon interactions causing the source to shroud itself with an electron-positron atmosphere. The efficiency of pair cascades in converting injected energy into electron-positron rest mass can reach levels of about 10% in static pair atmospheres. The emerging radiation is strongly modified by the pair atmosphere causing the spectrum to soften and to have characteristic breaks.For emission coming from a region near the Schwarzschild radius, L>10-3LEdd is sufficient to cause prolific pair production. Radiation pressure then drives a mildly relativistic pair wind with Compton drag limiting the Lorentz factor to be less then 10. The pair rest mass power is at most of the order of Lc.Most results so far on static pair atmospheres and pair winds are either qualitative or based on simple analytical models. Needed numerical treatments of both time dependent and steady radiative transfer of both the continuum and the annihilation line radiation in mildly relativistic flows are relevant not only for AGNs but also for gamma ray bursts and galactic black hole sources.

LIMITS TO THE PHYSICAL PARAMETERS IN EXTRAGALACTIC GAMMA-RAY SOURCES

2009 ◽  
Vol 18 (10) ◽  
pp. 1523-1527 ◽  
Author(s):  
E. V. DERISHEV
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
Physical Parameters ◽  
Gamma Ray Burst ◽  
Upper Limits

We examine several constraints on the physical parameters in active galactic nuclei and gamma-ray burst, originating from the assumption that these sources are efficient in converting their energy into gamma-rays. It is shown that in most cases these constraints may be reformulated in terms of bounds on the jet Lorentz factor, for which both the lower and the upper limits can be evaluated.

scholarly journals VLBA Imaging of a Large Sample of Blazars

1998 ◽  
Vol 164 ◽  
pp. 159-160
Author(s):  
J. M. Attridge ◽  
D. H. Roberts ◽  
J. F.C. Wardle
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Ambient Medium ◽  
Surrounding Medium ◽  
Galactic Nuclei ◽  
Large Sample ◽  
Field Lines ◽  
5 Ghz ◽  
The Magnetic Field

AbstractAs part of our continuing study of parsec-scale magnetic fields in active galactic nuclei we have obtained deep polarization-sensitive images of the blazar 1055+018 with the VLBA at 5 GHz. These dramatic images reveal a magnetized layer of material on the outer surfaces of the jet, distinct from the bulk of the jet. This morphology suggests interaction of the jet with the surrounding medium, the resulting shear stretching the magnetic field lines in the direction of the flow. Further multi-frequency polarization-sensitive observations of 1055+018 offer the opportunity to study radio jet-ambient medium interactions in detail.

scholarly journals Doppler Boosting Effect on the Jet Radiation of Gamma-Ray Bursts and Active Galactic Nuclei

2016 ◽  
Vol 12 (S324) ◽  
pp. 82-84
Author(s):  
Xiao-Li Huang ◽  
Hai-Ming Zhang ◽  
Shu-Qing Zhong ◽  
En-Wei Liang
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Lorentz Factor ◽  
High Energy ◽  
Mass Scale ◽  
Gamma Ray Bursts ◽  
Radiation Physics ◽  
Physical Laws ◽  
Bl Lacs

AbstractHigh energy photon radiations of gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) are dominated by their jet radiations. It was suggested that relativistic jets powered by different mass-scale black holes may share the same physical laws. A tight relation among the peak luminosity, the peak photon energy in the νfν spectrum, and the initial Lorentz factor is found for GRBs. With samples of GeV-TeV BL Lacs, FSRQs, and NLS1 galaxies, we show that these sources do not follow this relation. This may be attributed to the jet geometry and continuous/episodic jet as well as radiation physics for different kinds of sources.

scholarly journals Physical parameters of active galactic nuclei derived from properties of the jet geometry transition region

2020 ◽  
Vol 498 (2) ◽  
pp. 2532-2543
Author(s):  
E E Nokhrina ◽  
Y Y Kovalev ◽  
A B Pushkarev
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Common Property ◽  
Ambient Medium ◽  
Ambient Pressure ◽  
Galactic Nuclei ◽  
Physical Parameters ◽  
Pressure Amplitude ◽  
Black Hole Mass ◽  
Black Hole Spin

ABSTRACT We use the observed jet boundary transition from parabolic to conical shape, which was previously discovered to be a possible common property in active galactic nuclei, to estimate various parameters for black holes, jets and the ambient medium. We previously explained the geometry transition as a consequence of a change in the jet properties: a transition from a magnetically dominated to an equipartition regime. This interpretation allows us to estimate the black hole spin, the black hole mass and the ambient pressure amplitude, using the observed jet shape break position and the jet width at the transition point, for 11 active galactic nuclei. The black hole spin values obtained using our method are consistent with the lower estimates for sources with redshift z < 2 from spin evolution modelling. We find that the method of black hole mass determination based on the relationship between the broad-line region size and its luminosity may underestimate the masses of sources with large jet viewing angles. We propose a new method for the determination of the black hole mass, obtaining masses in the interval 108–1010 M⊙. The range of values of the ambient pressure amplitude points to the uniform medium conditions for the sources in our sample, with a tentative indication of higher pressure around Fanaroff–Riley II sources.

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