Evolution, speed, and precession of the parsec-scale jet in the 3C 84 radio galaxy

TL;DR

This study uses high-resolution 43 GHz imaging over a decade to analyze the complex evolution, speed, and precession of the parsec-scale jet in the radio galaxy 3C 84, revealing detailed internal structures and dynamic behavior.

Contribution

It introduces a novel high-resolution imaging method, eht-imaging, enabling detailed temporal analysis of jet kinematics and morphology in 3C 84.

Findings

Jet exhibits three distinct expansion regimes.

Detected irregular variation in jet launching direction.

Quantified jet expansion speeds and morphological transitions.

Abstract

We present high resolution images of the radio source 3C 84 at 43 GHz, from 121 observations conducted by the BEAM-ME monitoring program between 2010 and 2023. Imaging was performed using the recent forward modeling imaging method eht-imaging, which achieved a resolution of 80 $\mu$as, a factor of $\sim$2-3 better than traditional imaging methods such as CLEAN. The sequence of images depicts the growth and expansion of the parsec-scale relativistic jet in 3C 84, clearly resolving a complex internal structure, showing bending in the jet, and changes in its launching direction and expansion speed. We report measurements of the expansion speed in time, which show that the jet undergoes three regimes, marked by the beginning and ending of a hot spot frustration phase. The images' high resolution allows us also to measure the projected launching direction as a function of time, finding an irregular variation pattern. Our results confirm previous studies of the morphological transition underwent by 3C 84 and provide quantitative measurements of the jet's kinematic properties over a decade time-scale.