Acceleration and Energy Transport in the AGN jets: from sub-pc to kpc scale
Numerical Modeling of Electromagnetic Radiation from AGN Jets
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Transcript of Numerical Modeling of Electromagnetic Radiation from AGN Jets
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Numerical Modeling of Electromagnetic Radiation from AGN Jets
Based on
-ray emission and spectral evolution of pair plasmas in AGN jets
Bottcher et al. Astronomy and Astrophysics Vol. 324 1997
Giridhar Nandikotkur
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Numerical Modeling of Electromagnetic Radiation from AGN Jets
• What are Active Galactic Nuclei (AGN)? Structure Historical Existence
• Physical Processes Experiment leading to theory
a chronological journey Current Status of theoretical methods
• First step- a small one
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What are Active Galactic Nuclei (AGNs)?
• Historical Existence Extra-galactic
measured redshifts Extremely bright and violent
presence of jets at all wavelengths
Estimated energy more than of order of 10^60 ergs!
Something gravitational in nature Sharp rise in Luminosity towards the center
Massive object at the center-black hole?
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What are Active Galactic Nuclei (AGNs)?
• Structure Black hole at the center Accretion disc Jet Clouds at some distance Ordered magnetic filed lines emanating from BH
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Physical Processes• Synchrotron Radiation
suggested by polarization measurements
Experimentally observation: Power law energy spectrum
can be produced by power law distribution of electrons
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Physical Processes Photon Scattering by Inverse Comton
emission
Thompson scattering - non-relativistic
Compton Scattering - relativistic: Klein-Nishina
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Physical Processes• Broadband Spectrum
Synchrotron radiation has a peak and (dF/dlog) = F vs. will show a peak. Peak around optical-UVfalls towards UV, Xrays
• Compton Gamma Ray Observatory Launch 1991 Detection of sources with high energy gamma ray emission Bulk of their luminosity in Gamma rays A second peak in the broad band spectrum
Explanation by Inverse Compton emission
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Torus
BLR
Ac. Disk B. Hole
Electrons
Photons
SED for FSRQ
Peak 1: Synchrotron Radiation
Peak 2. Accretion Disk Black Body
Peak 3. Self Synchrotron Emission (SSC)
Peak 4. External Comption Disk (ECD)
Peak 5. External Compton clouds (ECC)
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Theoretical ApproachesNumerical Model.
Assume an injected leptonic (e+ e-)
plasma blob with power law distribution.
Evolution of photon and electron distributions using emission and absorption processes.
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Power Law: N()d = C -s dC: Normalization constant N()d = No
Energy Losses
(d /dt)synchrotron ; (d /dt)SSC ; Numerical Integration
(d /dt)ECD ; (d /dt)ECC ;
Change in particle distribution
t = 0 + t * (d /dt)ECD Forward Euler
Photon Spectrum at each time step
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Power Law distribution. Log-Log Plot
-1.50
-1.00
-0.50
0.00
0.50
0.0 2.0 4.0 6.0 8.0
Log(Gamma)
Lo
g(N
)
Power Law Distribution
0.0
2.0
4.0
6.0
0 5000 10000 15000 20000 25000
Gamma: Lorentz factor
N(G
am
ma
)
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Simulation of ECD process
Scattering of accretion disk photons of electrons
mathematica postscript
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Convergence of Trapezoidal Rule
-20
-15
-10
-5
0
5
10
0 2000 4000 6000 8000 10000 12000
Number of steps
Lo
g (
Dif
fere
nce
)
Cos(x) (0-Pi/2)
Cos(x) (0,Pi)
2x + 3x^2 +5x^4
Power Law
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Energy Loss Rate from Compton Scattering of Disk Radiation
-1
0
1
2
3
4
5
6
3 3.5 4 4.5 5 5.5 6 6.5
Lorentz factor of electrons
En
erg
y L
oss
Ra
te
ELR
Has to match exactly with the paper.If not, find the parameter that is differentin the initialization
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Future Work
• Include other processes.
• Generate Photon Spectrum
• Explore Gaussian Quadrature to Numerically integrate.
• Ambitious Target: 3 months!