"Photoionization simulations for the discriminating astrophysicist since 1978"
This is a copy of the Cloudy web site of many years ago. The current web site is
What is Cloudy?
Most of the quantitative information we have about the cosmos comes from spectroscopy. Examples include absorption lines superimposed on distant quasars by intervening galaxies or the intergalactic medium, emission lines in nebulae, and the emission lines of the quasars themselves. In turn many of these observations involve low-density gas, where the detailed ionization or gas kinetic temperature is determined by a host of microphysical balances rather than by a single temperature. Analytical solutions to the coupled set of equations are seldom possible, and numerical solutions are an aid to understand their physical properties.
Cloudy is designed to simulate these environments. For more information please see Quantitative spectroscopy of photoionized clouds, in the 2003 Annual Reviews Astronomy & Astrophysics, 41, 517, or Spectroscopic Challenges of Photoionized Plasmas, ASP Conference Series, vol. 247, edited by Gary Ferland and Daniel Wolf Savin for general reviews
A complete download of the code will include four sets of files. These include the source, a large set of atomic data files, the test suite used to validate the code's behavior on your system, and the documentation Hazy, which comes in three PDF files.
A version of the code will have a set of pages giving updates. The hot fixes page will list corrections that need to be made to the downloaded source. These are bug fixes that were not included in the version of the code used to generate the output from the test suite. So the hot fixes should be applied after the test suite has been run and your system validated. A problems page will list known problems with that version of the code, and the revision history page lists corrections made to that version.
The code is installed by a series of steps: a) download the files into four separate directories, b) edit the file "path.c" to tell the code where the atomic data will live, c) compile the source, d) download and compile any ancillary stellar atmosphere continua you will use, e) run the test suite and verify that your system works, f) apply the hot fixes.
The current stable version is C94.00. Follow this link to download and set up this version.
This is a summary of the links that appear at the top of each page. These pages contain links to many other pages or resources.
C94.00. links to information on the current stable version of the code.
Other versions contains links to old versions of the code, as well as development and bleeding edge versions. This includes beta 5 of c96, released 2003 Mar 30.
Revision history. This page summarizes improvements to the code.
The future: The code is still being developed! Its capabilities have always been limited by processor speed, which improves every year. Future plans are discussed here.
etcetera Miscellaneous information about the code, including FAQs, its history, style convention, acknowledgements, people involved in its development, computing at Cambridge in the 1970's, and what the version numbers mean, are all described. New! Added a discussion of the distinction between notation such as C+2 vs C III. (2003 May 9).
Acknowledgements for help with the code. This includes people who have developed code or discovered bugs, and the funding agencies that made it possible.
Contacts, mailing list; You can sign up for an email list if you would like to receive announcements of future releases. This includes a list of bad addresses that were dropped. It also says how to contact me
links; This includes software contributed to drive Cloudy, other spectral synthesis codes, development software, atomic data, Kentucky, meetings on spectroscopy, and a collection of cloud images from across the internet.
Site map, search contains an option to search the site and also a site map.