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M. Dietrich, F. Hamann (University of Florida)
Quasars are among the most luminous objects in the universe, and they can be studied in detail up to the highest known redshift. The age of the universe is approximately 1 Gyr or less for redshifts larger than z~q 4. In the context of galaxy formation and early star formation, there is growing evidence that quasar activity is closely connected with massive star formation in spheroidal systems (e.g., Kauffmann & Haehnelt 2000; Granato et al. 2001). Quasars can be used as tracers of the star formation history in the early universe provided that the gas associated with the quasar is closely related to the host galaxy. \alpha -elements, like oxygen or magnesium, are formed predominantly in massive stars on short time scales, while Fe has a dominant contribution from intermediate-mass stars via Type Ia SNe. The significantly different time scales result into an iron enrichment delay of the order of 1 Gyr. Therefore, emission line ratios of iron and \alpha -elements in early quasars can provide important information for dating the epoch of the first star formation episode and for determining the nature of the stellar population which enriched the gas seen in these quasars. We will discuss results of the investigation of the FeII/MgII2798 emission line ratio of high redshift quasars with redshifts up to z~q 5. Furthermore, the evolution of the FeII/MgII2798 emission line ratio will be studied as a function of redshift and luminosity.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.