On Synthetic Absorption Line Profiles of Thermally Driven Winds from
  Active Galactic Nuclei
  The warm absorbers observed in more than half of all nearby active galactic
nuclei (AGN) are tracers of ionized outflows located at parsec scale distances
from the central engine. If the smallest inferred ionization parameters
correspond to plasma at a few $10^4$~K, then the gas undergoes a transition
from being bound to unbound provided it is further heated to $\sim 10^6$~K at
larger radii. Dannen et al. recently discovered that under these circumstances,
thermally driven wind solutions are unsteady and even show very dense clumps
due to thermal instability. To explore the observational consequences of these
new wind solutions, we compute line profiles based on the one-dimensional
simulations of Dannen et al. We show how the line profiles from even a simple
steady state wind solution depend on the ionization energy (IE) of absorbing
ions, which is a reflection of the wind ionization stratification. To organize
the diversity of the line shapes, we group them into four categories: weak
Gaussians, saturated boxy profiles with and without an extended blue wing, and
broad weak profiles. The lines with profiles in the last two categories are
produced by ions with the highest IE that probe the fastest regions. Their
maximum blueshifts agree with the highest flow velocities in thermally unstable
models, both steady state and clumpy versions. In contrast, the maximum
blueshifts of the most high IE lines in thermally stable models can be less
than half of the actual solution velocities. Clumpy solutions can additionally
imprint distinguishable absorption troughs at widely separated velocities.
