Photoionization Codes

There are several codes commonly used to perform photoionization calculations for the photoionized gas in AGN. These include (in alphabetical order):

CLOUDY	Publically Distributed site: http://www.pa.uky.edu/~gary/cloudy Primary author: Gary Ferland One of the first (nearly 25 years old), and still probably the most commonly used code for a variety of astrophysical applications, including photoionized gas in AGN.
ION	Proprietary site: none Primary author: Hagai Netzer A code especially designed for the study of photoionized gas in the X-ray band.
XSTAR	Publically Distributed site: http://heasarc.gsfc.nasa.gov/docs/software/xstar/xstar.html Online Guide Primary author: Tim Kallman A code especially designed for the study of photoionized gas in the X-ray band. This code comes with the facility to make XSPEC "table models".

By necessity, all these codes have to make certain assumptions & approximations. Thus benchmark comparisons are regularly (occasionally ?) made of their outputs. For the latest results see proceedings of the "Plasma2000" workshop.