Radiation driven outflow in active galactic nuclei: the feedback effects
  of scattered and reprocessed photons
  We perform time-dependent, 2DHD numerical simulations to study the dynamics
of a slowly rotating accretion flow from sub-pc to pc scales under the
irradiation from the central AGN. Compared to previous work, we improve the
calculation of the radiative force due to X-rays. More importantly, in addition
to radiative pressure and radiative heating/cooling directly from the central
AGN, in the momentum equation we also include the force due to the scattered
and reprocessed photons. We find that the accretion flow properties change
significantly due to this "re-radiation" effect. The inflow rate at the inner
boundary is reduced, while the outflow rate at the outer boundary is enhanced
by about one order of magnitude. This effect is more significant when the
density at the outer boundary is higher. The properties of outflows such as
velocity, momentum and energy fluxes, and the ratio of outflow rate and the
accretion rate, are calculated. We find that the efficiency of transferring the
radiation power into the kinetic power of outflow is typically $10^{-3}$, far
below the value of $\sim 0.05$ which is assumed in some cosmological
simulations. The effect of the temperature of the gas at the outer boundary
($T_0$) is investigated. When $T_0$ is high, the emitted luminosity of the
accretion flow oscillates. This is because in this case the gas around the
Bondi radius can be more easily heated to be above the virial temperature due
to its high internal energy. Another question we hope to address is the
so-called "sub-Eddington" puzzle. Observationally, the luminosity of almost all
AGNs are sub-Eddington, while theoretically the luminosity of an accretion flow
can easily be super-Eddington. We find that even when the re-radiation effect
is included and outflow does become much stronger, the luminosity, while
reduced, can still be super-Eddington.
