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A.D. Forestell (SARA, UVa), M.D. Leising, V.P. Kulkarni (SARA, Clemson)
Analytic models for the chemical evolution of galaxies were fit to absorption system metal abundances derived from quasar spectra. The quasar spectra show absorption lines of several elements from objects between the quasars and Earth. The abundances in these objects, which we assume to be young galaxies, are determined from the spectra. Using a cosmological model to determine age from redshift, the variation of elemental abundances with age can be determined. The chemical evolution was modeled using standard equations for the mass of interstellar matter in an annulus of a disk galaxy and the mass fraction of a metal within. Making several assumptions (instantaneous recycling approximation, constancy of the initial mass function and stellar yields, linear dependence of birthrate on gas mass, and restricted forms of mass infall) yields models that can be solved analytically (e.g., Clayton 1985). Two methods were used to obtain the stellar elemental yields, the first using solar abundances and the second using calculated supernova yields (Woosley & Weaver 1995).
Data compiled from previous studies (Lu et al. 1996) were used, and additionally a spectrum from QSO1351 was analyzed. The quasar abundances, in particular that of zinc, were reasonably described by the analytic models, and most closely matched the method using SNII yields.
This work was supported by the NSF Research Experiences for Undergraduates (REU) Site Program through grant AST 96169939 to Florida Tech and the Southeastern Association for Research in Astronomy (SARA).
References:
Clayton, D.D. 1986, PASP, 98, 968.
Lu, L. et al. 1996, ApJS, 107, 475.
Woosley, S.E. and Weaver, T.A. 1995, ApJS, 101, 181.
The author(s) of this abstract have provided an email address for comments about the abstract: adf2e@virginia.edu