Qwind code release: a non-hydrodynamical approach to modelling
  line-driven winds in active galactic nuclei
  Ultraviolet (UV) line driven winds may be an important part of the active
galactic nucleus (AGN) feedback process, but understanding their impact is
hindered by the complex nature of the radiation hydrodynamics. Instead, we have
taken the approach pioneered by Risaliti & Elvis, calculating only ballistic
trajectories from radiation forces and gravity, but neglecting gas pressure. We
have completely re-written their QWIND code using more robust algorithms, and
can now quickly model the acceleration phase of these winds for any AGN
spectral energy distribution spanning UV and X-ray wavebands. We demonstrate
the code using an AGN with black hole mass $10^8\, M_\odot$ emitting at half
the Eddington rate and show that this can effectively eject a wind with
velocities $\simeq (0.1-0.2)\, c$. The mass loss rates can be up to $\simeq 0.3
M_\odot$ per year, consistent with more computationally expensive
hydrodynamical simulations, though we highlight the importance of future
improvements in radiation transfer along the multiple different lines of sight
illuminating the wind. The code is fully public, and can be used to quickly
explore the conditions under which AGN feedback can be dominated by accretion
disc winds.
