Software for the Analysis of Emission Line Nebulae

WFPC-2 Image of NGC 6543 courtesy of J.P. Harrington and NASA

Welcome to the Nebular Analysis Software Resources page. You may retrieve the nebular software, or run the tasks temden and ionic, which are both part of this package. These applications make use of the N-level atom approximation to compute electron temperature, density, ionic abunances, and other quantities for a low-density (i.e., nebular) gas. General information about the nebular package is available, as is detailed information about the N-level atom approximation.

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NEW!!New Version (2.0)

The nebular package has been substantially re-engineered since its last release. Many new features have been added, including the capability to compute line emissivities from more than 5 atomic levels, depending upon the availability of the supporting atomic data. The atomic data have all been updated to the most recent available. Moreover, the atomic data are stored in FITS binary tables (per ion), so that the user may update the atomic data as improved values appear in the literature.

Thirteen new ions of C, O, Ne, Na, Mg, Al, Si, S, Cl, K, and Ca have been added to the set of those previously supported, and as a consequence, 15 new electron density or temperature diagnostics are also available, which span a much greater range of density, temperature, and ionization.

The ntcontour task has been substantially enhanced, and has an interactive option. It is now possible to customize the diagnostic to the ratio of any of the available atomic transitions. This task is particularly useful for determining the range of N_e and T_e where a particular diagnostic is sensitive, for investigating non-traditional diagnostics, and for estimating the consequences of a given level of uncertainty in an observed line ratio.

You may obtain the nebular package by retreiving and installing the STSDAS package (V2.0 or later), or you may retrieve the nebular package for personal installation, provided you have TABLES (V2.0 or later) installed. All of this software is layered on IRAF, which can be obtained from NOAO.

Software Sampler

Fill-out forms are available to allow you to:

Run temden.
This task can calculate the electron temperature or density for a selected ion, given the ratio of the flux from the diagnostic emission lines.

Run ionic.
This task calculates line emissivities, level populations, and the abundance (relative to H+) for one of several ions, given the electron temperature and density.

Catalog of Emission Line Fluxes

The on-line "Catalog of Relative Emission Line Intensities Observed in Planetary Nebulae" (ELCAT for short) is an electronic listing of fluxes on over 1000 planetary nebulae that have been published in the astronomical literature through mid-1994. This catalog, and the ancillary information, are available for on-line browsing, WAIS searches, and retrieval through WWW and ftp.

About NEBULAR...

The nebular package was developed by Richard A. Shaw (Space Telescope Science Institute) and Reginald J. Dufour (Rice University). Much of the capability is based upon the fivel-level atom program FIVEL, published by De Robertis, Dufour, and Hunt (1987 JRASC, 81, 195). A paper describing the methodology and the scientific utility of this package appeared in Shaw and Dufour (1995, PASP, 107, 896); a preprint of this paper is available on-line and as compressed PostScript (161 KB).

This project was funded by the NASA Astrophysics Data Program through grant NAG5-1432 to Space Telescope Science Institute; supplemental funding was provided through an STScI internal research grant.

NEBULAR home page Ionic task Temden task

Copyright 1997 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.

Dick Shaw (

Last modified 21 February 2005