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M. Dietrich (University of Florida, Georgia State University), F. Hamann (University of Florida), J.C. Shields (Ohio University)
Quasars are among the most luminous objects in the universe which can be used to probe early epochs of the cosmic evolution. Assuming that the gas associated with quasars is closely related to their host galaxy, they provide valuable information about the chemical composition of the gas. Hence, based on the metallicity, quasars can be employed as tracers of the star formation history of their harboring galaxies. We have observed a sample of 70 quasars (3.5 \leq z \leq 5) to extend prior studies to higher redshifts and earlier epochs. This redshift range corresponds to an age of the universe of less than ~1\,Gyr. The prominent quasar emission-line spectrum provides several line ratios which are sensitive to metallicity variations as has been shown by Hamann et al. (2002). We use these line ratios which involve NV1240, CIV1549, HeII1640, OIII]1663, and NIII]1750 to estimate the chemical composition of the gas. The result, indicating at least solar up to several times solar metallicity, will be discussed in the context of star formation and galaxy evolution models.
MD and FH acknowledge support from NASA grant NAG\,5-3234 and NSF grant AST-99-84040.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.