A 20+ year overview of VLBI observations of the peculiar radio source 3C 84

The super-massive black holes (SMBH) located at the centres of AGN often launch highly relativistic jets. The main jet launching scenarios are either due to magnetic field lines anchored to the accretion disk (Blandford & Payne 1982) or directly connected to the black hole’s (BH) ergosphere (Blandford & Znajek 1977), and are an ongoing, hot topic of active research.
Very long baseline interferometry (VLBI), and specifically at millimetre wavelengths, offers an unparalleled view into the physical processes in action, in the close vicinity of BHs. Owing to its proximity and only moderate Doppler-boosting, the nearby radio-galaxy 3C 84 (NGC 1275) is a very suitable target for VLBI observations at the highest frequencies and spatial resolutions. Utilising archival and our own millimetre-VLBI observations of 3C 84 obtained over the past 20+ years, we can trace the VLBI jet of 3C 84 down to scales of ∼100 Schwarzschild radii, facilitating the study of jet formation and acceleration. Our observations reveal a limb brightened, double-rail structure reaching deep into the core region. As part of this analysis we also associate jet component ejection events with the multi-wavelength variability light-curves at radio frequencies and gamma-rays. Furthermore, by cross-correlating these light-curves, which span a time frame of 40+ years, we determine time-lags and draw conclusions regarding the location of the high energy emission at the jet base. Finally, we constrain the magnetic field strength and structure. In this talk I will give an overview of more than four decades of VLBI observations of 3C 84 and then present new results from recent global VLBI imaging campaigns.