Cloudy and Associates
Spectral simulations for the discriminating astrophysicist since 1978

Frequently-used links

Instructions for downloading and installing the release version are here

Just want the code?  The release version is here.  The download includes Hazy, the code's documentation.

Links to the hotfixes and known problems web pages.

Cloudy's revision history is here.

The Cloudy discussion board is here.

Frequently asked questions are here.

The Cloudy News page lists changes and updates.

Other questions?  Please post queries on the discussion board.

What is Cloudy?

Most of the quantitative information we have about the cosmos comes from spectroscopy. In many cases the light we analyze was produced by atoms in the first generations of stars and galaxies.  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. The spectra are produced by dilute gas where such properties as the gas kinetic temperature, chemical state, level of ionization, and level populations, are determined by a host of microphysical processes rather than by a single temperature. Analytical solutions are seldom possible and computer solutions are needed to understand their physical properties.

Numerical simulations make it possible to understand complex physical environments starting from first principles.  Cloudy is designed to do exactly this.  For more information please see Quantitative spectroscopy of photoionized clouds, in the 2003 Annual Reviews Astronomy & Astrophysics, 41, 517 (available here), the research monograph  Spectroscopic Challenges of Photoionized Plasmas, ASP Conference Series, vol. 247, edited by Gary Ferland and Daniel Wolf Savin, or the graduate text Osterbrock & Ferland Astrophysics of Gaseous Nebulae and Active Galactic Nuclei (the publisher's web site is here).

Recent developments on this web site

Spring 2008  Moved to the Cloudy News page

A list of typos in AGN3 is posted here.  (2007 July 19)

Christophe Morisset has posted a description of his Cloudy 3D tools on astro-ph.  His web site is here.  His tools are IDL wrappers that drives Cloudy to create 3D nebulae.  The following image is an example and more are in this paper.:

The effects of a time-variable continuum source are included, a project done in collaboration with Will Henney and Robin Williams and an outgrowth of Henney et al. (2005, ApJ, 621, 328, on the ADS here).  Nick Abel has created a pair of animated gifs showing the time evolution of an H⁺ region with PDR after its ionizing star is turned off and then turned back on.  The first animation shows the cloud recombining and becoming molecular and the second shows the hydrogen ionization front moving across the cloud.  Time dependent continuum sources will be included in the next major upgrade, due in early 2007.

Recent publications

The 2nd edition of Astrophysics of Gaseous Nebulae by Osterbrock & Ferland  is described here - they offer a slight discount off the retail price.  A list of typos is here.

He I iso-electronic sequence  Porter & Ferland (2007, ApJ, 664, 586, on astro ph here) describe the He-like iso-electronic sequence.  Porter et al. (2005, ApJ, 622, 73L), describe the treatment of the He⁰ atom and the He I emission spectrum.  Also available on astro-ph here.  Bauman et al., (2005, ApJ, 628, 541) give a more complete description of the effects on singlet-triplet mixing, also available on astro-ph here.  More information and additional tables are available on Ryan Porter's web site.

He I emission.  The physics is described in Porter et al. (ApJ, 657, 327, ApJ, 622L, 73) and Bauman et al. (ApJ 628, 541).

PDR Physics  Abel et al. (ApJS, 161, 65-95) present self-consistent calculations of the spectrum, chemistry, and structure of an H II region and its associated PDR.  It is also on astro-ph here and a high resolution version here.

H₂ Physics  Shaw et al. (ApJ, 624, 794) describe molecular hydrogen in Cloudy.  It is also available on astro-ph here or as a high resolution version here.

Dynamics  Henney et al. (ApJ, 621, 328) describe the treatment of dynamics in the current version of Cloudy.  Also available from astro-ph here.

Grains  van Hoof et al (MNRAS 350, 1330) describe the current treatment of grain physics. Also available from astro-ph here.

Other pages on this web site

The future:  The code is still being developed!  Its capabilities have always been  limited by processor speed and the atomic/molecular data base.  All of these improve every year.  Future plans are discussed here.

Acknowledgements for help with the code.  This includes people who have developed code or discovered bugs, and the funding agencies that made it possible.

etcetera  Miscellaneous information, including the following:  FAQs, acknowledgements, people involved in its development, the code's history and style convention, computing at Cambridge in the 1970's, what the version numbers mean, the distinction between notation such as C⁺² vs C III, how to call C from Fortran.  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.

Last changed 02/04/08.
Return to the Cloudy Home Page.
Copyright 1978-2006 Gary J. Ferland