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M. L. Houdashelt (Johns Hopkins University), S. C. Trager (Kapteyn Astronomical Institute, Netherlands), G. Worthey (Washington State University), R. A. Bell (University of Maryland)
We present new calculations of synthetic Lick indices, building upon the previous work of Tripicco & Bell (1995, AJ, 110, 3035; hereafter TB95). TB95 calculated synthetic Lick indices for three solar-metallicity stars -- a cool giant, a turnoff star, and a cool dwarf -- and examined how these indices change as both overall metallicity and the abundances of ten elements are varied individually. Other groups have used these results (in a differential sense) to estimate how the integrated Lick indices of populations of stars having non-solar abundance ratios would differ from those of stellar populations having solar abundance ratios. Since the time of Tripicco & Bell's analysis, two important developments have occurred. First, the computer code and spectral line lists used to calculate the synthetic spectra have been revised and updated. For example, the TiO bands, not included in TB95, have been studied extensively and are now incorporated in the models. Second, four new Lick indices have been defined that measure the strengths of two hydrogen lines, H\gamma and H\delta, which have proven to be good age indicators in the integrated light of stellar populations. In this poster, we present updated calculations of synthetic Lick indices for the same three stars examined by TB95, compare the resulting index values to those predicted by the empirically-derived Lick index fitting functions, and examine the sensitivity of the synthetic indices, including those for H\gamma and H\delta, to changes in overall metallicity and changes in the abundances of C, N, O, Mg, Fe, Ca, Na, Si, Cr, and Ti.
The author(s) of this abstract have provided an email address for comments about the abstract: mlh@pha.jhu.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.