The 2013 Release of Cloudy
  This is a summary of the 2013 release of the plasma simulation code Cloudy.
Cloudy models the ionization, chemical, and thermal state of material that may
be exposed to an external radiation field or other source of heating, and
predicts observables such as emission and absorption spectra. It works in terms
of elementary processes, so is not limited to any particular temperature or
density regime. This paper summarizes advances made since the last major review
in 1998. Much of the recent development has emphasized dusty molecular
environments, improvements to the ionization / chemistry solvers, and how
atomic and molecular data are used. We present two types of simulations to
demonstrate the capability of the code. We consider a molecular cloud
irradiated by an X-ray source such as an Active Nucleus and show how treating
EUV recombination lines and the full SED affects the observed spectrum. A
second example illustrates the very wide range of particle and radiation
density that can be considered.
