GLOBAL STRUCTURE OF THREE DISTINCT ACCRETION FLOWS AND OUTFLOWS AROUND BLACK HOLES FROM TWO-DIMENSIONAL RADIATION-MAGNETOHYDRODYNAMIC SIMULATIONS

Abstract

We present the detailed global structure of black hole accretion flows and\noutflows through newly performed two-dimensional radiation-magnetohydrodynamic\nsimulations. By starting from a torus threaded with weak toroidal magnetic\nfields and by controlling the central density of the initial torus, rho_0, we\ncan reproduce three distinct modes of accretion flow. In model A with the\nhighest central density, an optically and geometrically thick supercritical\naccretion disk is created. The radiation force greatly exceeds the gravity\nabove the disk surface, thereby driving a strong outflow (or jet). Because of\nthe mild beaming, the apparent (isotropic) photon luminosity is ~22L_E (where\nL_E is the Eddington luminosity) in the face-on view. Even higher apparent\nluminosity is feasible if we increase the flow density. In model B with a\nmoderate density, radiative cooling of the accretion flow is so efficient that\na standard-type, cold, and geometrically thin disk is formed at radii greater\nthan ~7R_S (where R_S is the Schwarzschild radius), while the flow is\nradiatively inefficient otherwise. The magnetic-pressure-driven disk wind\nappears in this model. In model C the density is too low for the flow to be\nradiatively efficient. The flow thus becomes radiatively inefficient accretion\nflow, which is geometrically thick and optically thin. The magnetic-pressure\nforce, in cooperation with the gas-pressure force, drives outflows from the\ndisk surface, and the flow releases its energy via jets rather than via\nradiation. Observational implications are briefly discussed.\n