S. K. Keating, J. E. Everett, S. C. Gallagher, R. P. Deo
An integral part of the Unified Model for Active Galactic Nuclei (AGNs) is an
axisymmetric obscuring medium, which is commonly depicted as a torus of gas and
dust surrounding the central engine. However, a robust, dynamical model of the
torus is required in order to understand the fundamental physics of AGNs and
interpret their observational signatures. Here we explore self-similar, dusty
disk-winds, driven by both magnetocentrifugal forces and radiation pressure, as
an explanation for the torus. Using these models, we make predictions of AGN
infrared (IR) spectral energy distributions (SEDs) from 2-100 microns by
varying parameters such as: the viewing angle; the base column density of the
wind; the Eddington ratio; the black hole mass; and the amount of power in the
input spectrum emitted in the X-ray relative to that emitted in the UV/optical.
We find that models with N_H,0 = 10^25 cm^-2, L/L_Edd = 0.1, and M_BH >= 10^8
Msun are able to adequately approximate the general shape and amount of power
expected in the IR as observed in a composite of optically luminous Sloan
Digital Sky Survey (SDSS) quasars. The effect of varying the relative power
coming out in X-rays relative to the UV is a change in the emission below ~5
micron from the hottest dust grains; this arises from the differing
contributions to heating and acceleration of UV and X-ray photons. We see mass
outflows ranging from ~1-4 Msun/yr, terminal velocities ranging from ~1900-8000
km/s, and kinetic luminosities ranging from ~1x10^42-8x10^43 erg/s. Further
development of this model holds promise for using specific features of observed
IR spectra in AGNs to infer fundamental physical parameters of the systems.
View original:
http://arxiv.org/abs/1202.4681
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