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C. M. Church, S. E. Woosley (University of California, Santa Cruz), A. Heger (Los Alamos National Lab)
We study the chemical evolution of the Milky Way galaxy at early times and low metallicities using a set of approximately 350 models of zero metallicity massive stars. The stars, which span a mass range from 10 to 260 solar masses and include pair instability supernovae, have been evolved from their birth on the main sequence through their deaths as supernovae using a nuclear reaction network of up to 1800 isotopes. The yields from the explosions have been incorporated into a modified version of the Timmes chemical evolution code. The effects of varying the shape of the IMF have been examined. Results are compared to the Cayrel et al data set for [Z] \approx -3 stars as well as to recent observations of extremely metal poor stars. Overall, the agreement with these data sets is quite good though there are notable discrepancies at Cr and Sc. We find no clear diagnostic of pair instability supernovae, but on the other hand, no clear evidence against their presence with an abundance suggested by the extrapolation of a Salpeter IMF to high masses. Similarly, we find no clear evidence for a ``hypernova" (KE ~ 10**52 erg) component in the stars between 10 and 100 solar masses.
This work has been supported by the NSF (AST-02-06111).
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.