Self-consistent spectra from radiative GRMHD simulations of accretion on to Sgr A*

Abstract

We present the first spectral energy distributions produced self-consistently by 2.5D general relativistic magnetohydrodynamical (GRMHD) numerical simulations, where radiative cooling is included in the dynamical calculation. As a case study, we focus on the accretion flow around the supermassive black hole in the Galactic Centre, Sagittarius A* (Sgr A*), which has the best constrained physical parameters. We compare the simulated spectra to the observational data of Sgr A* and explore the parameter space of our model to determine the effect of changing the initial magnetic field configuration, the ion-to-electron temperature ratio Ti/Te and the target accretion rate. We find the best description of the data for a mass accretion rate of ∼10−9 M⊙ yr−1, and rapid spin (0.7 < a* < 0.9). The submillimetre peak flux seems largely independent of initial conditions, while the higher energies can be very sensitive to the initial magnetic field configuration. Finally, we also discuss flaring features observed in some simulations, which may be due to artefacts of the 2D configuration.