On the diversity and complexity of absorption line profiles produced by outflows in Active Galactic Nuclei. (arXiv:1208.6044v1 [astro-ph.CO])

On the diversity and complexity of absorption line profiles produced by outflows in Active Galactic Nuclei. (arXiv:1208.6044v1 [astro-ph.CO]):
Understanding the origin of AGN absorption line profiles and their diversity
could help to explain the physical structure of the accretion flow, and also to
assess the impact of accretion on the evolution of the AGN host galaxies. Here
we present our first attempt to systematically address the issue of the origin
of the complexities observed in absorption profiles. Using a simple method, we
compute absorption line profiles against a continuum point source for several
simulations of accretion disk winds. We investigate the geometrical,
ionization, and dynamical effects on the absorption line shapes. We find that
significant complexity and diversity of the absorption line profile shapes can
be produced by the non-monotonic distribution of the wind velocity, density,
and ionization state. Non-monotonic distributions of such quantities are
present even in steady-state, smooth disk winds, and naturally lead to the
formation of multiple and detached absorption troughs. These results
demonstrate that the part of a wind where an absorption line is formed is not
representative of the entire wind. Thus, the information contained in the
absorption line is incomplete if not even insufficient to well estimate gross
properties of the wind such as the total mass and energy fluxes. In addition,
the highly dynamical nature of certain portions of disk winds can have
important effects on the estimates of the wind properties. For example, the
mass outflow rates can be off up to two orders of magnitude with respect to
estimates based on a spherically symmetric, homogeneous, constant velocity
wind.