Astrophysics

Early Metal Production in the Universe

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Science  17 Aug 2001:
Vol. 293, Issue 5533, pp. 1223-1225
DOI: 10.1126/science.293.5533.1223e

To understand the chemical evolution of the universe, astronomers use spectroscopy and photometry to determine the abundances of heavier elements (metals). Metals are created by stellar nucleosynthesis and supernovae, and their abundances can be used to estimate the amount and rate of star formation. Co, for example, is overabundant relative to Fe in metal-poor systems, such as Galactic bulge and thick-disk stars, that may have formed early in the universe. This overabundance may be produced by the fastest evolving stars.

Given the implications about star formation rates suggested by the overabundance of Co, Ellison et al. measured Co in damped Lyman alpha systems (DLAs). A DLA is a region of high hydrogen density that lies between a very distant bright quasar and the observer. In these very distant regions, Co is overabundant relative to Fe. Thus, this Co signature suggests that star formation was probably rapid in the early universe and would also be consistent with the Co-overabundant metal-poor systems being formed at about the same time, confirming that Galactic bulge and thick-disk stars are old. — LR

Mon. Not. R. Astron. Soc.326, 628 (2001).

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