Early Star Formation Traced by the Highest Redshift Quasars
نویسنده
چکیده
The iron abundance relative to α-elements in the circumnuclear region of quasars is regarded as a clock of the star formation history and, more specifically, of the enrichment by type Ia supernovae (SNIa). We investigate the iron abundance in a sample of 22 quasars in the redshift range 3.06. We also detect a population of weak iron emitters at z∼4.5, which are possibly hosted in systems that evolved more slowly. Alternatively, the trend of the FeII/MgII ratio at high redshift may reflect significantly different physical conditions of the circumnuclear gas in such high redshift quasars. Subject headings: quasars: emission lines — galaxies: evolution, high-redshift
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