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

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 <ns0:monospace>eht-imaging</ns0:monospace>; it achieved a resolution of 80 μas, which is a factor of ∼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; it clearly shows a complex internal structure with bending in the jet and changes in its launching direction and expansion speed. We report measurements of the expansion speed over time, which show that the jet goes through three regimes, marked by the start and end of a hot spot frustration phase. The high resolution of the images also allowed us to measure the projected launching direction as a function of time, and we find an irregular variation pattern. Our results confirm previous studies of the morphological transition undergone by 3C 84 and provide quantitative measurements of the jet’s kinematic properties over a decade-long timescale.