Lorentz factor distribution of blazars from the optical Fundamental plane of black hole activity

TL;DR

This paper introduces a novel method to determine the Lorentz factor distribution of blazars using the optical fundamental plane, providing insights into jet physics without relying on apparent jet speeds.

Contribution

The study presents a new approach to estimate blazar Lorentz factors via the optical fundamental plane, avoiding traditional methods dependent on jet speed measurements.

Findings

Lorentz factor distribution follows a power law with index -2.1.

Range of Lorentz factors is from 1 to 40.

Method offers an independent estimate of jet boosting parameters.

Abstract

Blazar radiation is dominated by a relativistic jet which can be modeled at first approximation using just two intrinsic parameters - the Lorentz factor $\Gamma$ and the viewing angle $\theta$. Blazar jet observations are often beamed due to relativistic effects, complicating the understanding of these intrinsic properties. The most common way to estimate blazar Lorentz factors needs the estimation of apparent jet speeds and Doppler beaming factors. We present a new and independent method of constructing the blazar Lorentz factor distribution, using the optical fundamental plane of black hole activity. The optical fundamental plane is a plane stretched out by both the supermassive black holes and the X-ray binaries, in the 3D space provided by their [OIII] line luminosity, radio luminosity and black hole mass. We use the intrinsic radio luminosity obtained from the optical fundamental plane to constrain the boosting parameters of the VLBA Imaging and Polarimetry Survey (VIPS) blazar sample. We find a blazar bulk Lorentz factor distribution in the form of a power law as $N(\Gamma) \propto \Gamma^{-2.1 \pm 0.4}$ for the $\Gamma$ range of 1 to 40. We also discuss the viewing angle distribution of the blazars and the dependence of our results on the input parameters.