Revision of two-temperature magnetically arrested flows onto a black hole

Abstract

We revisit the radiative properties of 3D general relativistic magnetohydrodynamics (GRMHD) two-temperature magnetically arrested disk (MAD) models in which electrons are heated by a magnetic turbulent cascade. We focus on studying the model emission, whose characteristics include variability in both total intensity and linear/circular polarizations as well as rotation measures at energies around the synchrotron emission peak in millimeter waves. We find that radiative properties of MAD models with turbulent electron heating are well converged with respect to the numerical grid resolution, which has not been demonstrated before. We compare radiation from two-temperature simulations with turbulent heating to single-temperature models with electron temperatures calculated based on commonly used $R~(\beta)$ prescription. We find that the self-consisitent two-temperature models with turbulent heating do not significantly outperform the $R~(\beta)$ models and, in practice, may be indistinguishable from the $R~(\beta)$ models. Accounting for physical effects such as radiative cooling and nonthermal electron distribution function makes a weak impact on properties of millimeter emission. Models are scaled to Sgr A*, an accreting black hole in the center of our galaxy, and compared to the most complete observational datasets. We point out the consistencies and inconsistencies between the MAD models and observations of this source and discuss future prospects for GRMHD simulations.