The imprints of AGN feedback within a supermassive black hole's sphere
  of influence
  We present a new 300 ks Chandra observation of M87 that limits pileup to only
a few per cent of photon events and maps the hot gas properties closer to the
nucleus than has previously been possible. Within the supermassive black hole's
gravitational sphere of influence, the hot gas is multiphase and spans
temperatures from 0.2 to 1 keV. The radiative cooling time of the lowest
temperature gas drops to only 0.1-0.5 Myr, which is comparable to its free fall
time. Whilst the temperature structure is remarkably symmetric about the
nucleus, the density gradient is steep in sectors to the N and S, with
$\rho{\propto}r^{-1.5\pm0.1}$, and significantly shallower along the jet axis
to the E, where $\rho{\propto}r^{-0.93\pm0.07}$. The density structure within
the Bondi radius is therefore consistent with steady inflows perpendicular to
the jet axis and an outflow directed E along the jet axis. By putting limits on
the radial flow speed, we rule out Bondi accretion on the scale resolved at the
Bondi radius. We show that deprojected spectra extracted within the Bondi
radius can be equivalently fit with only a single cooling flow model, where gas
cools from 1.5 keV down below 0.1 keV at a rate of 0.03 M$_{\odot}$/yr. For the
alternative multi-temperature spectral fits, the emission measures for each
temperature component are also consistent with a cooling flow model. The lowest
temperature and most rapidly cooling gas in M87 is therefore located at the
smallest radii at ~100 pc and may form a mini cooling flow. If this cooling gas
has some angular momentum, it will feed into the cold gas disk around the
nucleus, which has a radius of ~80 pc and therefore lies just inside the
observed transition in the hot gas structure.
