Plasma effects on relativistic pair beams from TeV blazars: PIC simulations and analytical predictions

Pair beams produced by very-high-energy radiation from TeV blazars emit gamma rays in the GeV band by inverse-Compton scattering of soft photons. The observed GeV-band signal is smaller than that expected from the full electromagnetic cascade. This means that the pair beams must be affected by other...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2017-11, Vol.607, p.A112
Main Authors: Rafighi, I., Vafin, S., Pohl, M., Niemiec, J.
Format: Article
Language:English
Subjects:
Blazars
Computer simulation
Elastic scattering
Energy
galaxies: active
Gamma rays
gamma rays: general
instabilities
Magnetic fields
Mathematical models
Particle beams
Particle in cell technique
Photons
plasmas
Process parameters
relativistic processes
waves
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Summary:Pair beams produced by very-high-energy radiation from TeV blazars emit gamma rays in the GeV band by inverse-Compton scattering of soft photons. The observed GeV-band signal is smaller than that expected from the full electromagnetic cascade. This means that the pair beams must be affected by other physical processes reducing their energy flux. One possible loss mechanism involves beam-plasma instabilities that we consider in the present work. For realistic parameters the pair beams cannot be simulated by modern computers. Instead, we use a simple analytical model to find a range of the beam parameters that (i) provides a physical picture similar to that of realistic pair beams and (ii) at the same time can be handled by available computational resources. Afterwards, we performed corresponding two-dimensional (2D) particle-in-cell (PIC) simulations. We confirm that the beams experience only small changes in the relevant parameter regime, and other processes such as deflection in magnetic field must be at play.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/201731127