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

TL;DR

This study presents self-consistent spectral energy distributions from 2.5D GRMHD simulations of Sgr A*, including radiative cooling, to better match observational data and understand accretion physics.

Contribution

It introduces the first self-consistent spectra from radiative GRMHD simulations of Sgr A* with radiative cooling included in the dynamics.

Findings

Best fit with accretion rate ~1e-9 Msun/yr and high spin (0.7-0.9).

Submillimeter flux is insensitive to initial magnetic conditions.

Higher energy spectra are sensitive to initial magnetic field configuration.

Abstract

We present the first spectral energy distributions produced self-consistently by 2.5D general relativistic magneto-hydrodynamical (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, ion to electron temperature ratio T_i/T_e and the target accretion rate. We find the best description of the data for a mass accretion rate of ~ 1e-9 Msun/yr, and rapid spin (0.7 < a_* < 0.9). The submillimeter 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, that may be due to artifacts of the 2D configuration.