The relation between black hole masses and Lorentz factors of the jet components in blazars

Abstract

We explore the relation between black hole mass ($M_{\rm BH}$) and the motion of the jet components for a sample of blazars. The Very Long Baseline Array (VLBA) 2cm Survey and its continuation: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments (MOJAVE) have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements on their apparent velocities of jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A significant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components, which the Eddington ratio is only weakly correlated with the minimal Lorentz factor, which may imply that the Blandford-Znajek (BZ) mechanism may dominate over the Blandford-Payne (BP) mechanism for the jet acceleration (at least) in blazars.