Black hole powered GRMHD jet and jet synchrotron image on horizon scale

General relativistic magnetohydrodynamic (GRMHD) flows along magnetic fields threading a black hole can be divided into inflow and outflow parts. When the inflow becomes Poynting flux–dominated (PFD), the black hole rotational energy can be extracted outward. By assuming that the dominating (electromagnetic) component of the energy flux per flux tube is conserved at the surface where the inflow and outflow are separated, the outflow part of the solution can be constrained by the inflow part. Based on the above idea, we present a self-consistent, semi-analytical jet model for a cold, PFD GRMHD flow along a parabolic streamline.  Preliminary results of  the computed jet synchrotron images on horizon scale based on ray-tracing in Kerr spacetime, and general relativistic radiative transfer are also presented. Such studies are important for future sub-mm VLBI observations, whose resolution (~20 micro-arcsec) is high enough to resolve the horizon of the supermassive black hole at the center of, e.g., M87.