Software for the Analysis of Emission Line Nebulae

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©1995. Astronomical Society of the Pacific
107: 896-906, 1995 September

Software for the Analysis of Emission-Line Nebulae

Richard A. Shaw
Space Telescope Science Institute (1), 3700 San Martin Dr., Baltimore, MD 21218
Electronic mail:

Reginald J. Dufour
Dept. of Space Physics & Astronomy, Rice University, Houston, TX 77251
Electronic mail:

Received 1995 March 3; accepted 1995 May 26


A set of software tools has been developed for the IRAF/STSDAS environment to derive the physical conditions in a low-density (nebular) gas given appropriate diagnostic emission line ratios; and line emissivities given appropriate emission line fluxes, the electron temperature (T) and density (N ). The package is based on the five-level atom program developed by De Robertis, Dufour and Hunt (1987), but it includes diagnostics from a greater set of ions and emission lines, most particularly those in the satellite ultraviolet that are now observable. Two of the applications make use of a 3-zone nebular model to derive T and N simultaneously in separate zones of low-, intermediate-, and high-ionization. These applications are useful for calculating nebular densities and temperatures directly from the traditional diagnostic line ratios, either to provide some reasonable input parameters for a more complicated physical model, or to calculate ionic abundances (or other quantities) within some simplifying assumptions. Examples of the utility of these diagnostics for real nebulae are presented.

Subject headings: Computing and Data Analysis; Interstellar Medium and Nebulae

(1) Operated by the Association of Universities for Research in Astronomy, Inc. under contract NAS5-26555 from the National Aeronautics and Space Administration.

Rocio Katsanis
Thu Aug 8 17:23:06 EDT 1996