BAL QSOs and Extreme UFOs: the Eddington connection
  We suggest a common physical origin connecting the fast, highly ionized winds
(UFOs) seen in nearby AGN, and the slower and less ionized winds of BAL QSOs.
The primary difference is the mass loss rate in the wind, which is ultimately
determined by the rate at which mass is fed towards the central supermassive
black hole (SMBH) on large scales. This is below the Eddington accretion rate
in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143,
but ranges up to $\sim 10-50$ times this in BAL QSOs. For UFOs this implies
black hole accretion rates and wind mass loss rates which are at most
comparable to Eddington, giving fast, highly-ionized winds. In contrast BAL QSO
black holes have mildly super-Eddington accretion rates, and drive winds whose
mass loss rates are significantly super-Eddington, and so are slower and less
ionized. This picture correctly predicts the velocities and ionization states
of the observed winds, including the recently-discovered one in SDSS
J1106+1939. We suggest that luminous AGN may evolve through a sequence from BAL
QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors
drop during the decay of a bright accretion event. LoBALs correspond to a
short-lived stage in which the AGN radiation pressure largely evacuates the
ionization cone, but before the large-scale accretion rate has dropped to the
Eddington value. We show that sub-Eddington wind rates would produce an $M -
\sigma$ relation lying above that observed. We conclude that significant SMBH
mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme
UFOs, or obscured from direct observation.
