Grain Physics and IR Dust Emission in AGN Environments
  We study the effects of a detailed dust treatment on the properties and
evolution of early-type galaxies containing central black holes, as determined
by AGN feedback. We find that during cooling flow episodes, radiation pressure
on the dust in and interior to infalling shells of cold gas can greatly impact
the amount of gas able to be accreted and therefore the frequency of AGN
bursts. However, the overall hydrodynamic evolution of all models, including
mass budget, is relatively robust to the assumptions on dust. We find that IR
re-emission from hot dust can dominate the bolometric luminosity of the galaxy
during the early stages of an AGN burst, reaching values in excess of $10^{46}$
erg/s. The AGN-emitted UV is largely absorbed, but the optical depth in the IR
does not exceed unity, so the radiation momentum input never exceeds $L_{\rm
BH}/c$. We constrain the viability of our models by comparing the AGN duty
cycle, broadband luminosities, dust mass, black hole mass, and other model
predictions to current observations. These constraints force us to models
wherein the dust to metals ratios are $\simeq 1%$ of the Galactic value, and
only models with a dynamic dust to gas ratio are able to produce both quiescent
galaxies consistent with observations and high obscured fractions during AGN
"on" phases. During AGN outbursts, we predict that a large fraction of the FIR
luminosity can be attributed to warm dust emission ($\simeq100$ K) from dense
dusty gas within $\leq 1$ kpc reradiating the AGN UV emission.
