Blazars SED in Conical Plasma Flow : a Monte Carlo study

TL;DR

This study models blazar broadband emission using a Monte Carlo approach to simulate anisotropic conical plasma flows, successfully reproducing observed spectra and variability, and exploring the influence of emission region geometry.

Contribution

It introduces a novel Monte Carlo method to simulate blazar SEDs in anisotropic plasma flows, accounting for geometry and variability effects.

Findings

Reproduces SEDs of specific blazars like 3C 454.3, OJ 287, S5 0716+714, PKS 2155-304.

Shows low synchrotron peak blazars can be explained by SSC with R/L < 0.01.

Demonstrates degeneracy between particle density and emission region length in variability modeling.

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 $\langle \gamma^{ran} \rangle$ $<<$ than the average component along the jet axis $\langle \gamma \rangle$. 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.