Speaker
Description
In this talk, I will review our recent progress and important findings of the beaming effect and relativistic jet property in gamma-ray blazars detected by the Fermi-Large Area Telescope (Fermi-LAT). Blazars are a particular class of radio-loud Active Galactic Nucleus (AGNs), characterized by many distinctive observational properties, which are due to the relativistic beaming effect. Since the beaming effect is not observable and the origin of jets is still not clear, we proposed several methods to reveal these important issues from different perspectives, based on our derived large sample of Fermi blazars. Principally, we come to the results and conclusions as follows:
(1) We present an effective method by means of the beaming effect to estimate four crucial parameters, including the upper limit of central black hole mass M, the Doppler factor , the location of γ-ray-emitting region Rγ, and the propagation angle with respect to the axis of the accretion disk , for more than 800 gamma-ray blazars. We put forward an updated demarcation between BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) based on the relation between broad-line region luminosity and disk luminosity both measured in Eddington units, i.e., L$_{\rm disk}$/L$_{\rm Edd}$ = 4.68x10$^{-3}$, indicating that there are some differences between BL Lacs and FSRQs on the accretion power in the disk. Besides, for the first time, we proposed a so-called “appareling zone”, which stands for a potential transition field between BL Lacs and FSRQs where changing-look blazars may reside. We found five confirmed changing-look sources in our sample that are lying in this zone.
(2) We made use of information from emission lines, spectral energy distributions, and the beam radio luminosity to study the jet power, black hole mass and spin. Our results suggest that BL Lac jets are powered by extracting BH rotation energy, while FSRQ jets are mostly powered by accretion disks. We also claim that the launching of the relativistic jet is dominated by the Blandford-Znajek process for both FSRQs and BL Lacs.
(3) By adopting a two-component model of emission within jets, we successfully separated the emission of radio, X-ray, GeV and TeV into beamed and unbeamed contributions for the largest sample of Fermi blazars up to now. Our results suggest that the emission is mainly from the core/beamed component in gamma-ray blazars.
