IZI: Inferring metallicities (Z) and Ionization parameters (q)


IZI is an IDL function that uses Bayesian inference to derive the metallicity (Z) and ionization parameter (q) of an ionized nebula given a set of observed emission line fluxes and an input photo-ionization model grid. The method is described in Blanc et al. 2015. IZI permits the use of an arbitrary set of SELs in the determination of Z and q and allows the inclusion of flux upper limits. The method provides a self-consistent way of determining the physical conditions of ionized nebulae from strong emission lines (SELs) that is not tied to the arbitrary choice of a particular line ratio diagnostic and makes use of all the available information. Unlike theoretically calibrated SEL diagnostics the method is flexible and not tied to a particular photo-ionization model.


IZI can be downloaded from an SVN repository by typing the following command in a terminal:

> svn checkout svn://carrot.obs.carnegiescience.edu/izi/trunk izi

This will create a directory called "izi" which contains the source code "izi.pro" and a directory containing different input photo-ionization model grids in IZI format (FITS tables). Sufficient documentation to run the code is provided in the header of the "izi.pro" file.

In case the SVN repository is down you can get the code and grids here


You need to add the two following lines to your .cshrc file before using IZI:

> setenv IZI_DIR /yourpath/izi

> setenv IDL_PATH $IDL_PATH{:}+${IZI_DIR}


If you publish results that make use of IZI please reference the following publication:

Blanc et al. 2015, "IZI: Inferring the Gas Phase Metallicity (Z) and Ionization Parameter (q) of Ionized Nebulae using Bayesian Statistics"


IZI is written and mantained by Guillermo A. Blanc. If you find bugs or errors in the documentation please forward them to me at gblancm at obs.carnegiescience.edu.