Hada, Kazuhiro

Probing the inner jet of M87; from the jet base to HST-1.

Relativistic jets in active galactic nuclei are one of the most energetic phenomena in the Universe. While it is widely accepted that AGN jets are powered by accretion onto the supermassive black hole, the detailed processes of jet formation as well as production of high-energy emission up to TeV gamma-ray still remain as major questions in current astrophysics.

The giant radio galaxy M87 accompanies one of the nearest AGN jets showing intense radiation through radio to TeV gamma-ray. Its proximity and the large mass of the central black hole provide an excellent advantage to probe the sites of jet formation and gamma-ray production. VLBI observations at radio frequencies are a unique tool to resolve such regions directly. In this talk, I will present the latest progress of our study for the innermost part of the M87 jet based on multi-frequency, multi-epoch VLBI observations. We especially focus on the two remarkable regions; the jet base near the black hole and the peculiar jet feature HST-1 at a large distance from the jet base.  Physical properties of these features obtained from the observations will be discussed.