Doppler boosting effect and flux evolution of superluminal components in QSO 3C345

TL;DR

This study models the kinematics and flux evolution of superluminal components in QSO 3C345 using a precessing jet-nozzle scenario, demonstrating a strong correlation between Doppler boosting and observed flux changes.

Contribution

It introduces a precessing jet-nozzle model with a 7.30-year period to accurately simulate superluminal component trajectories and flux evolution in QSO 3C345.

Findings

Kinematic properties are well modeled by the precession scenario.

Flux variations correlate strongly with Doppler boosting profiles.

Short-term flux fluctuations may be due to intrinsic source variability.

Abstract

The precessing jet-nozzle scenario previously proposed was applied to interpret the VLBI-measured kinematics of five superluminal components (C4,C5,C9,C10 and C22) and their flux density evolution in blazar 3C345. It is shown that in the inner-trajectory sections their kinematic properties, including trajectory,coordinates, core separation and apparent velocity can be well model-simulated by using the scenario with a precession period of 7.30yr (4.58yr in the source frame) and a precessing common trajectory, which produces the individual knot-trajectories at their corresponding precession phases. Through the model-simulation of their kinematic behavior their bulk Lorentz factor ,viewing angle and Doppler factor were derived as functions of time. These anticipatively-determined Lorentz/Doppler factors were used to investigate the knots' Doppler-boosting effect and interpret their flux evolution. It was found that the light-curves of the five superluminal components observed at 15, 22 and 43GHz were extraordinarily well coincident with their Doppler boosting profiles. Additionally, some flux fluctuations on shorter time-scales could be due to variations in knots' intrinsic flux and spectral index. The close relation between the flux evolution and the Doppler boosting effect not only firmly validates the precessing jet-nozzle scenario being fully appropriate to explain the kinematic and emission properties of superluminal components in QSO 3C345, but also strongly supports the traditioal common point-view: superluminal components are physical entities (shocks or plasmoids) participating relativistic motion toward us with acceleration/deceleration along helical trajectories.