Spectra of Three-Dimensional Magnetized Accretion Flows

Abstract

We examine if three-dimensional (3D) magnet-hydrodynamical (MHD) accretion flow, which is proposed as a model for low-luminosity active galactic nuclei (LLAGNs) and Galactic black hole candidates (BHCs), can reproduce the observed data of Sagittarius A* (Sgr A*). The emergent spectra are calculated by the Monte Carlo radiative transfer simulations. It is found that the 3D MHD flow is successful in reproducing the basic properties of the observed spectrum of Sgr A* on the condition that the emission from the innermost part of the flow ( r< 10rs) is dominant, where rs is the Schwarzschild radius. §1. MHD accretion flows The black-hole accretion disks turn into optically-thin high-temperature flows in the case that the mass-accretion rate is much less than the critical value. In such flows, the magnetic hydrodynamical effects have significant influence on the accretion structure as well as the emergent spectra. The global 3D MHD simulations have been performed and revealed the considerably complicated flow pattern (Matsumoto 1999; Hawley 2000; Machida, Hayashi, and Matsumoto 2000). Although the 3D MHD flows are considered to be a realistic model, the test of the flows in comparison with the observations, surprisingly, has been poorly attempted.