Chandra X-ray observations of the giant elliptical galaxy M87 resolve the thermal state of the hot interstellar medium into the accretion ( Bondi ) radius of its central 3 \times 10 ^ { 9 } M _ { \odot } black hole .
We measure the X-ray gas temperature and density profiles and calculate the Bondi accretion rate , \dot { M } _ { Bondi } \sim 0.1 M _ { \odot } yr ^ { -1 } .
The X-ray luminosity of the active nucleus of M87 observed with Chandra is L _ { x, 0.5 - 7 { \thinspace keV } } \sim 7 \times 10 ^ { 40 } erg s ^ { -1 } .
This value is much less than the predicted nuclear luminosity , L _ { Bondi } \sim 5 \times 10 ^ { 44 } erg s ^ { -1 } , for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10 % .
If the black hole in M87 accretes at this rate it must do so at a much lower radiative efficiency than the canonical value .
The multiwavelength spectrum of the nucleus is consistent with that predicted by an advection-dominated flow .
However , as is likely , the X-ray nucleus is dominated by jet emission then the properties of flow must be modified , possibly by outflows .
We show that the overall energetics of the system are just consistent with the predicted Bondi nuclear power .
This suggests that either most of the accretion energy is released in the relativistic jet or that the central engine of M87 undergoes on-off activity cycles .
We show that , at present , the energy dumped into the ISM by the jet may reduce the accretion rate onto the black hole by a factor \propto ( v _ { j } / c _ { s } ) ^ { -2 } , where v _ { j } is the jet velocity and c _ { s } the ISM sound speed , and that this is sufficient to account for the low nuclear luminosity .