Abstract :
Certain fractions of active galactic nuclei (AGNs) show structured relativistic jets and rapid variability at all electromagnetic wavelengths. While many theoretical models suggest how AGNs can convert the gravitational energy of accreting matter onto the central supermassive black holes (SMBHs) to radiation and outflows, detailed physical mechanisms responsible for determining physical properties near the black holes, the onset of relativistic jets and generation of very high energy particles remain elusive yet. In this talk, I will present our ongoing research, primarily using high-resolution VLBI techniques at the millimeter bands (e.g., EHT and GMVA with ALMA) and in space (RadioAstron) in combination with multi-wavelength observations from radio to gamma-rays. Various results from nearby sources, such as M87 and those from other radio galaxies, neutrino blazars, and peculiar spiral galaxies, will be presented. Also, I will briefly introduce the efforts of Korean astronomy communities for forthcoming observing facilities such as the extended Korean VLBI Network, next-generation EHT, Millimetron, Square Kilometer Array, and the Korean Neutrino Observatory.
