Accretion onto Black Holes from Large Scales Regulated by Radiative
  Feedback. II. Growth Rate and Duty Cycle
  This paper, the second of a series on radiation-regulated accretion onto
black holes (BHs) from galactic scales, focuses on the effects of radiation
pressure and angular momentum of the accreting gas. We simulate accretion onto
intermediate-mass black holes, but we derive general scaling relationships that
are solutions of the Bondi problem with radiation feedback valid for any mass
of the BH $M_{\rm bh}$. Thermal pressure of the ionized sphere around the BH
regulates the accretion rate producing periodic and short-lived luminosity
bursts. We find that for ambient gas densities exceeding $n^{\rm cr}_{\rm
H,\infty} \propto M_{\rm bh}^{-1}$, the period of the oscillations decreases
rapidly and the duty cycle increases from 6%, in agreement with observations of
the fraction of active galactic nuclei at $z\sim 3$, to 50%. The mean accretion
rate becomes Eddington limited for $n_{\rm H,\infty}>n_{\rm H,\infty}^{\rm Edd}
\simeq n_{\rm H,\infty}^{\rm cr} T_{\infty,4}^{-1}$ where $T_{\infty,4}$ is the
gas temperature in units of $10^4$ K. In the sub-Eddington regime, the mean
accretion rate onto BHs is about $1% T_{\infty,4}^{2.5}$ of the Bondi rate,
thus is proportional to the thermal pressure of the ambient medium. The period
of the oscillations coincides with depletion timescale of the gas inside the
ionized bubble surrounding the BH. Gas depletion is dominated by a pressure
gradient pushing the gas outward if $n_{\rm H,\infty}<n^{\rm cr}_{\rm
H,\infty}$ and by accretion onto the BH otherwise. Generally, for $n_{\rm
H,\infty}<n^{\rm cr}_{\rm H,\infty}$ angular momentum does not affect
significantly the accretion rate and period of the oscillations.
