The Relativistic Jet and Central Engine of Fermi Blazars

Abstract

Abstract The origin of jets is one of the most important issues concerning active galactic nuclei, yet it has remained obscure. In this work, we made use of information from emission lines, spectral energy distributions, and Fermi–LAT γ-ray emission to construct a blazar sample that contains 667 sources. We note that jet power originations are different for BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs). The correlation between jet power P jet and the normalized disk luminosity L Disk/L Edd shows a slope of −1.77 for BL Lacs and a slope of 1.16 for FSRQs. The results seem to suggest that BL Lac jets are powered by extracting black hole (BH) rotation energy, while FSRQ jets are mostly powered by accretion disks. Meanwhile, we find the accretion ratio M ̇ / M ̇ Edd increases with the normalized γ-ray luminosity. Based on this, we propose a dividing line, log ( L BLR / L Edd ) = 0.25 log ( L γ / L Edd ) − 2.23 , to separate FSRQs and BL Lacs in the diagram of L BLR/L Edd against L γ /L Edd using a machine-learning method; the method gives an accuracy of 84.5%. In addition, we propose an empirical formula, M BH / M ☉ ≃ L γ 0.65 / 21.46 , to estimate BH mass based on a strong correlation between γ-ray luminosity and BH mass. Strong γ-ray emission is typical in blazars, and the emission is always boosted by a Doppler-beaming effect. In this work, we generate a new method to estimate a lower limit of Doppler factor δ and give δ BL Lac = 7.94 and δ FSRQ = 11.55.