We present axisymmetric numerical simulations of radiatively inefficient accretion flows onto black holes combining general relativity , magnetohydrodynamics , self-consistent electron thermodynamics , and frequency-dependent radiation transport .
We investigate a range of accretion rates up to 10 ^ { -5 } \dot { M } _ { \mathrm { Edd } } onto a 10 ^ { 8 } M _ { \odot } black hole with spin a _ { \star } = 0.5 .
We report on averaged flow thermodynamics as a function of accretion rate .
We present the spectra of outgoing radiation and find that it varies strongly with accretion rate , from synchrotron-dominated in the radio at low \dot { M } to inverse Compton-dominated at our highest \dot { M } .
In contrast to canonical analytic models , we find that by \dot { M } \approx 10 ^ { -5 } \dot { M } _ { \mathrm { Edd } } , the flow approaches \sim 1 \% radiative efficiency , with much of the radiation due to inverse Compton scattering off Coulomb-heated electrons far from the black hole .
These results have broad implications for modeling of accreting black holes across a large fraction of the accretion rates realized in observed systems .