On the Virialization of Disk Winds: Implications for the Black Hole Mass Estimates in AGN. (arXiv:1306.1090v1 [astro-ph.GA])

On the Virialization of Disk Winds: Implications for the Black Hole Mass Estimates in AGN. (arXiv:1306.1090v1 [astro-ph.GA]):
[abbreviated] Estimating the mass of a supermassive black hole (SMBH) in an
active galactic nucleus (AGN) usually relies on the assumption that the broad
line region (BLR) is virialized. However, this assumption seems invalid in BLR
models that consists of an accretion disk and its wind. The disk is likely
Keplerian and therefore virialized. However, the wind material must, beyond a
certain point, be dominated by an outward force that is stronger than gravity.
Here, we analyze hydrodynamic simulations of four different disk winds: an
isothermal wind, a thermal wind from an X-ray heated disk, and two line-driven
winds, one with and the other without X-ray heating and cooling. For each
model, we check whether gravity governs the flow properties, by computing and
analyzing the volume-integrated quantities that appear in the virial theorem:
internal, kinetic, and gravitational energies, We find that in the first two
models, the winds are non-virialized whereas the two line-driven disk winds are
virialized up to a relatively large distance. The line-driven winds are
virialized because they accelerate slowly so that the rotational velocity is
dominant and the wind base is very dense. For the two virialized winds, the
so-called projected virial factor scales with inclination angle as 1/
\sin^2{i}. Finally, we demonstrate that an outflow from a Keplerian disk
becomes unvirialized more slowly when it conserves the gas specific angular
momentum -- as in the models considered here, than when it conserves the
angular velocity -- as in the so-called magneto-centrifugal winds.