Accretion and Outflow in Active Galaxies
  I review accretion and outflow in active galactic nuclei. Accretion appears
to occur in a series of very small--scale, chaotic events, whose gas flows have
no correlation with the large--scale structure of the galaxy or with each
other. The accreting gas has extremely low specific angular momentum and
probably represents only a small fraction of the gas involved in a galaxy
merger, which may be the underlying driver.
  Eddington accretion episodes in AGN must be common in order for the
supermassive black holes to grow. I show that they produce winds with
velocities $v \sim 0.1c$ and ionization parameters implying the presence of
resonance lines of helium-- and hydrogenlike iron. The wind creates a strong
cooling shock as it interacts with the interstellar medium of the host galaxy,
and this cooling region may be observable in an inverse Compton continuum and
lower--excitation emission lines associated with lower velocities. The shell of
matter swept up by the shocked wind stalls unless the black hole mass has
reached the value $M_{\sigma}$ implied by the $M - \sigma$ relation. Once this
mass is reached, further black hole growth is prevented. If the shocked gas did
not cool as asserted above, the resulting (`energy-driven') outflow would imply
a far smaller SMBH mass than actually observed. Minor accretion events with
small gas fractions can produce galaxy-wide outflows, including fossil outflows
in galaxies where there is little current AGN activity.
