Balancing Turbulent Heating with Radiative Cooling in Blazars

TL;DR

This paper develops a turbulent jet model for blazars based on PIC simulation extrapolations, successfully matching observed spectra and revealing key physical parameters of the emission region.

Contribution

It extends PIC simulation results to higher magnetizations and applies them to construct a comprehensive model of blazar emission spectra.

Findings

Good agreement with observed spectra of low-synchrotron peaked blazars.

LSP blazars are moderately Poynting flux dominated with specific magnetization and Lorentz factors.

Turbulent regions are located near or beyond the broad line region in jets.

Abstract

Recently, particle in cell (PIC) simulations have shown that relativistic turbulence in collisionless plasmas can result in an equilibrium particle distribution function where turbulent heating is balanced by radiative cooling of electrons. Strongly magnetized plasmas are characterized by higher energy peaks and broader particle distributions. In relativistically moving astrophysical jets, it is believed that the flow is launched Poynting flux dominated and that the resulting magnetic instabilities may create a turbulent environment inside the jet, i.e., the regime of relativistic turbulence. In this paper, we extend previous PIC simulation results to larger values of plasma magnetization by linearly extrapolating the diffusion and advection coefficients relevant for the turbulent plasmas under consideration. We use these results to build a single zone turbulent jet model that is based on the global parameters of blazar emission region, and consistently calculate the particle distribution and resulting synchrotron and inverse Compton emission spectra. We then test our model by comparing its predictions with the broad-band quiescent emission spectra of a dozen blazars. Our results show good agreement with observations of low-synchrotron peaked (LSP) sources and find that LSPs are moderately Poynting flux dominated with magnetization $1\lesssim \sigma \lesssim 5$, have bulk Lorentz factor $\Gamma\sim 10-30$, and that the turbulent region is located at the edge, or just beyond, the broad line region (BLR). The turbulence is found to be driven at an area comparable to the jet cross section.