Introducing EMILI: Computer‐aided Emission Line Identification

The identification of spectral lines can be a tedious process requiring theinterrogation of large spectroscopic databases, but it does lend itself tosoftware algorithms that can determine the characteristics of candidate lineidentifications. We present here criteria used for the identification of linesand a logic developed for a line identification software package called EMILI,which uses the v2.04 Atomic Line List as the basic line database. EMILIconsiders all possible database transitions within the wavelength uncertaintiesfor observed optical emission lines and computes an approximate intensity foreach candidate line. It searches for other multiplet members that are expectedto be seen with each candidate line, and rank orders all of the tentative lineidentifications for each observed line based on a set of criteria. When appliedto the spectra of the Orion Nebula and the planetary nebula IC 418, EMILI'srecommended line ID's agree well with those of previous traditional manual lineassignments. The existence of a semi-automated procedure should give impetus tothe study of very high signal-to-noise spectra, enabling the identification ofpreviously unidentified spectral lines to be handled with ease and consistency.Comment: 53 pages, 4 tables, 1 figure, accepted for publication in ApJ