Characterizing the emission region property of blazars

TL;DR

This study uses a large dataset of spectral energy distributions to statistically analyze the emission region properties of blazars, revealing differences between FSRQs and BL Lacs, and insights into jet physics and emission region locations.

Contribution

It provides the first large-sample statistical analysis of blazar emission regions within the leptonic one-zone framework, highlighting key differences between blazar subclasses.

Findings

FSRQs have lower electron energies than BL Lacs.

BL Lacs tend to have jets closer to magnetic equipartition.

One-third of blazars can produce Kelvin-Helmholtz instability.

Abstract

The studies and constraints on the emission region are crucial to the blazar radiation mechanism. Yet the previous works mainly focus on individual sources. In this work, we make use of the largest and the latest spectral energy distribution (SED) fitting results in the literature to statistically study the blazar emission region property in the framework of leptonic one-zone. Our results reveal (1) FSRQs show lower electron energy ($\gamma_{\rm p} \lesssim 1.6 \times 10^{3}$) than BL Lacs and tend to have a stronger magnetic field ($B$) and smaller electron-to-magnetic energy ratio ($U_{\rm e}/U_{\rm B}$) than BL Lacs; (2) we find the electro-magnetic equipartition would rather happen in the jets of BL Lacs than happen in the jets of FSRQs; (3) there are 682 blazars with a magnetic field weaker critical value of generating the Kelvin-Helmholtz instability, thus one-third of the blazars in our sample are able to produce this instability; (4) the distance ($d_{\rm em}$) between the emission region and the central black hole (BH) is in the scale of $\sim$0.1 pc, the location of the emission region may be evenly distributed inside and outside the broad line region (BLR).