Balancing turbulent heating with radiative cooling in blazars

• Published in: Monthly notices of the Royal Astronomical Society Vol. 513; no. 4; pp. 5766 - 5779
• Main Authors: Davis, Zachary, Rueda-Becerril, Jesús M, Giannios, Dimitrios
• Format: Journal Article
• Language: English
• Published: Oxford University Press 28.05.2022
• Subjects: radiation mechanisms: non-thermal; quasars: general; BL Lacertae objects: general; turbulence; acceleration of particles
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stac1282

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 the blazar emission region, and consistently calculate the particle distribution and the resulting 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 ≲ σ ≲ 5, have bulk Lorentz factor Γj ∼ 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.