Bondi flow from a slowly rotating hot atmosphere
  A supermassive black hole in the nucleus of an elliptical galaxy at the
centre of a cool-core group or cluster of galaxies is immersed in hot gas.
Bondi accretion should occur at a rate determined by the properties of the gas
at the Bondi radius and the mass of the black hole. X-ray observations of
massive nearby elliptical galaxies, including M87 in the Virgo cluster,
indicate a Bondi accretion rate Mdot which roughly matches the total kinetic
power of the jets, suggesting that there is a tight coupling between the jet
power and the mass accretion rate. While the Bondi model considers non-rotating
gas, it is likely that the external gas has some angular momentum, which
previous studies have shown could decrease the accretion rate drastically. We
investigate here the possibility that viscosity acts at all radii to transport
angular momentum outward so that the accretion inflow proceeds rapidly and
steadily. The situation corresponds to a giant Advection Dominated Accretion
Flow (ADAF) which extends from beyond the Bondi radius down to the black hole.
We find solutions of the ADAF equations in which the gas accretes at just a
factor of a few less than Mdot. These solutions assume that the atmosphere
beyond the Bondi radius rotates with a sub-Keplerian velocity and that the
viscosity parameter is large, alpha~0.1. The infall time of the ADAF solutions
is no more than a few times the free-fall time. Thus the accretion rate at the
black hole is closely coupled to the surrounding gas, enabling tight feedback
to occur. We show that jet powers of a few per cent of Mdot c^2 are expected if
either a fraction of the accretion power is channeled into the jet or the black
hole spin energy is tapped by a strong magnetic field pressed against the black
hole by the pressure of the accretion flow.(Truncated)
