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Radiatively inefficient accretion flows (RIAFs) are believed to powersupermassive black holes (SMBH) in the underluminous cores of galaxies. Suchblack holes are typically accompanied by flat-spectrum radio cores indicatingthe presence of moderately relativistic jets. One of the best constrained RIAFsis associated with the SMBH in the Galactic center, Sgr A*. Since the plasma inRIAFs is only weakly collisional, the dynamics and the radiative properties ofthese systems are very uncertain. Here we want to study the impact of varyingelectron temperature on the appearance of accretion flows and jets. Using 3-DGRMHD accretion flow simulations, we use ray tracing methods to predict spectraand radio images of RIAFs allowing for different electron heating mechanisms inthe in- and outflowing parts of the simulations. We find that small changes inthe electron temperature can result in dramatic differences in the relativedominance of jets and accretion flows. Application to Sgr A* shows that radiospectrum and size of this source can be well reproduced with a model whereelectrons are more efficiently heated in the jet. The X-ray emission issensitive to the electron heating mechanism in the jets and disk and thereforeX-ray observations put strong constraints on electron temperatures and geometryof the accretion flow and jet. For Sgr A*, the jet model also predicts asignificant frequency-dependent core shift which could place independentconstraints on the model once measured accurately. We conclude that moresophisticated models for electron distribution functions are crucial forconstraining GRMHD simulations with actual observations. For Sgr A*, the radioappearance may well be dominated by the outflowing plasma. Nonetheless, at thehighest radio frequencies, the shadow of the event horizon should still bedetectable with future Very Long Baseline Interferometric observations.

Observational appearance of inefficient accretion flows and jets in 3D GRMHD simulations: Application to Sgr~A*