The M87 Jet Rosetta Stone of AGN Jets

We investigate the structure and dynamics of the M87 jet based on multi-frequency VLBI observations and MHD jet theories. Millimeter VLBI cores are considered as innermost jet emissions. The jet structure up to similar to 10(5) r(s) is described as a parabolic streamline, indicating the lateral expansion under a confinement by the stratified ISM. Thus, the jet collimation maintains in five orders of magnitude in the distance starting from the vicinity of the supermassive black hole (SMBH), less than 10 r(s). We here examine the jet parabolic structure in order to identify the property of a bulk acceleration; observed sub-to-superluminal motions indicate an MHD acceleration from non-relativistic to relativistic regimes. We propose that the M87 jet consists of Poynting-flux dominated flows, powered by nonlinear torsional Alfven waves. Future sub-mm VLBI observations play an important role in resolving the origin of the M87 jets.