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Paper: Low-luminosity black holes: The case of M87
Volume: 290, Active Galactic Nuclei: from Central Engine to Host Galaxy
Page: 391
Authors: di Matteo, T.; Allen, S. W.; Fabian, A. C.; Wilson, A. S.; Young, A. J.
Abstract: Chandra observations of nearby galactic nuclei have allowed us to make significant progress in understanding why their central supermassive black holes are so dim. We examine the constraints on accretion disk models and on fuelling of the central black hole (and its relation to jet activity) for the nucleus of the giant elliptical galaxy M87, one of the most illustrative object within the class of low luminosity nuclei. Chandra X-ray observations of M87, for the first time, resolve the thermal state of the hot interstellar medium within the accretion (Bondi) radius of its central 3 times 109 Modot black hole. This implies a Bondi accretion rate, dotMBondi ∼0.1 Modotyr-1. The X-ray luminosity of the active nucleus of M87 observed with Chandra is Lx ∼7 times 1040 erg s-1. This greatly exceeds the predicted nuclear luminosity, LBondi ∼5 times 1044 erg s-1, for accretion at the Bondi rate with a canonical accretion radiative efficiency of 10%. We show that low radiative efficiency accretion flow models are consistent with the observations. However, the predicted Bondi nuclear power is consistent with the overall energetics of the system (and in particular with the kinetic energy of the jet). This suggests that either most of the accretion energy is released in the 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 sufficiently to account for its low luminosity.
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