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

TL;DR

This study finds a significant correlation between black hole masses and jet Lorentz factors in blazars, suggesting the Blandford-Znajek mechanism may primarily drive jet acceleration in these objects.

Contribution

It establishes a new intrinsic correlation between black hole mass and jet Lorentz factors in blazars, highlighting the potential dominance of the BZ mechanism in jet acceleration.

Findings

Significant correlation between black hole mass and jet Lorentz factors.

Weak correlation between Eddington ratio and Lorentz factors.

Implication that BZ mechanism may dominate jet acceleration.

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.