From nebular to pynebular: a new package for the analysis of emission lines

V. Luridiana (1,2), C. Morisset (1,2,3), R.A. Shaw (4), D. Díaz-González (5)

(1) Instituto Astrofísico de Canarias, La Laguna, Tenerife, Spain. (2) Universidad de La Laguna, Tenerife, Spain. (3) Instituto de Astronomía, UNAM, México DF, México. (4) NOAO, Tucson, Arizona, USA. (4) Shidix Technologies, Tenerife, Spain.

The nebular package is a widely used set of IRAF applications for the analysis of emission lines. It can be used in several ways to compute physical quantities and abundances given observed emission line intensities. For example, it can compute electron temperature (Te) and density (Ne), predict volume emissivities given Te and Ne, and ionic abundances given Te, and Ne, and one or more emission lines. In this contribution we describe an ongoing project to migrate {nebular} from IRAF to a more modern programming environment where it can be used as a stand-alone program, as a software library, or as a set of web applications.

Python, an interpreted, high-level programming language which enjoys wide use in the astronomical community, was selected as the target language. The current functionality of nebular will be preserved in the new environment, and the supporting atomic data will be reviewed and updated. Additionally, the current functionalities will be extended and new ones will be added. The following are a few examples: for a selected subsample of ions, the user will be given the option to switch among different data sets; atomic parameters for additional ions will be included, particularly those elements produced via s-process in AGB stars; a tool for the simultaneous determination of Ne and Te from pairs of line ratios will be added; the automated tasks such as ‘zones’ and ‘abund’, which can process observations of a long list of targets, will be extended to include infrared lines. Additional, basic functionalities are planned, such as computing ionic abundances for He and some other elements from recombination lines; recipes for computing total elemental abundances from ionic abundances will be added, using common or user-defined ICF formulae; and a tool for the error analysis of Te, Ne, and abundances will be developed.

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