  The discovery of hard, power-law X-ray emission from a sample of six nearby
elliptical galaxies, including the dominant galaxies of the Virgo,Fornax and
Centaurus clusters (M87, NGC 1399 and NGC 4696, respectively), and NGC 4472,
4636 and 4649 in the Virgo cluster, has important implications for the study of
quiescent supermassive black holes. We describe how the broad band spectral
energy distributions of these galaxies, which accrete from their hot gaseous
halos at rates comparable to their Bondi rates, can be explained by
low-radiative efficiency accretion flows in which a significant fraction of the
mass, angular momentum and energy is removed from the flows by winds. The
observed suppression of the synchrotron component in the radio band and the
systematically hard X-ray spectra, which are interpreted as thermal
bremsstrahlung emission, support the conjecture that significant mass outflow
is a natural consequence of systems accreting at low-radiative efficiencies. We
briefly discuss an alternative model for the X-ray emission, namely that it is
due to nonthermal synchrotron-self Compton processes in the accretion flow, or
wind. This appears to require implausibly weak magnetic fields. Emission from a
collimated jet viewed off axis should be distinguishable from the
bremsstrahlung model by variability and thermal line emission studies. We argue
that the difference in radiative efficiency between the nuclei of spiral and
elliptical galaxies arises from the different manner in which interstellar gas
is fed into the nuclei. In ellipticals, matter fed from the hot (slowly
cooling) ISM is likely to be highly magnetized and with low specific angular
momentum, both of which favor low-radiative efficiency accretion solutions and
possibly the formation of the observed jets.
