Blazars SED in Conical Plasma Flow : a Monte Carlo study

Abstract

Blazars host the most powerful persistent relativistic conical jet-a highly collimated anisotropic flow of material/plasma. Motivated by this, we explore the blazar's broadband spectral energy distribution (SED) in an anisotropic flow of plasma which emits via synchrotron and inverse Compton (IC) mechanism. The flow is conical with two velocity components: a highly relativistic flow component along the jet axis and a random perpendicular component with average random Lorentz factor γ ran << than the average component along the jet axis γ . Assuming a broken power-law electron population, we calculated the broadband SED using synchrotron and IC processes assuming a cylindrical (of radius R and length L) emission region. For the IC process, we used Monte Carlo approach. We found that such anisotropic flow can reproduce blazars broadband emission as well as general short and high amplitude variability, indicating that spectral and temporal variability are not sufficient to distinguish among existing models. We demonstrate this by reproducing SEDs of FSRQ 3C 454.3 and three BL Lacs objects OJ 287, S5 0716+714, PKS 2155-304. Our formalism and set-up also allow us to investigate the effect of the geometry and dimension of emission region on observed broadband spectra. We found that the SEDs of low synchrotron peak (LSP) blazar can be explained by considering only SSC (synchrotron self-Compton) if R/L (< 0.01), broadly mimicking a spine-sheath geometry. In general, the degeneracy between non-thermal particle number density and length of the emission region (L) allow us to reproduce any variability in terms of particle number density.

Plane polarisation in Comptonization process: A Monte Carlo study

“…The different steps involved are, case I: the incident photons are along the z-axis (i.e. θ i = 0) and the scattering plane is fixed to the considered emergent meridian plane; case III: the incident photon direction is fixed, say (θ i ,φ i ) and all possible scattering planes are considered; case IV: the incident photon lies on the surface of cone of opening angle θ i with having all possible scattering planes; and last a general case, Case V. In particular the case IV may be relevant for the external Comptonization in blazars of radio jet of opening angle θ i (Kumar & Kushwaha 2021), for example, here for θ i = 15 • the maximum emergent photons escape with θ s ∼25 • and have PD ∼ 0.06.…”

“…In addition, for low kT e (or non-relativistic electrons) one needs a large scattering number to generate the Wien spectrum, while for large kT e (relativistic electron) one need comparatively small scattering number (e.g. Kumar & Kushwaha 2021). We compute the Wien spectrum for Model 1 and 2 with N SC = 170 and 45, respectively.…”