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W. L. W. Sargent (Palomar Observatory, California Institute of Technology)
Stars in the Galactic halo have heavy element abundances as low as 1/10,000 of that in the sun. Below Fe/H ~ 1/300 of the solar value there is an increasing scatter in the relative abundances of various elements, including rare cases of very large overabundances of r-process elements perhaps synthesized in a single supernova. The overall distribution of r-process elements is thought to point to two early origins, one of them in primordial, supermassive stars. Metal-poor stars in nearby dwarf galaxies also give important information on early nucleosynthesis in metal-poor environments.
Studies of the absorption lines in the spectra of QSOs at very high redshifts, particularly the Damped Lyman-alpha absorbers, are yielding new information on the relative abundances of several elements and on the scatter in different lines of sight. I summarize this information and describe how it can be combined with the results derived from old stars to produce a picture of where and how the first heavy elements were synthesized.
This work was supported by the National Science Foundation under Grant AST-9900733.