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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. Numerical Modeling of Electromagnetic Radiation from AGN Jets. - PowerPoint PPT Presentation
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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
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
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?
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
Physical Processes• Synchrotron Radiation
suggested by polarization measurements
Experimentally observation: Power law energy spectrum
can be produced by power law distribution of electrons
Physical Processes Photon Scattering by Inverse Comton
emission
Thompson scattering - non-relativistic
Compton Scattering - relativistic: Klein-Nishina
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
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)
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.
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
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
)
Simulation of ECD process
Scattering of accretion disk photons of electrons
mathematica postscript
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
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
Future Work
• Include other processes.
• Generate Photon Spectrum
• Explore Gaussian Quadrature to Numerically integrate.
• Ambitious Target: 3 months!