Quasar Evolution and Star Formation History

Abstract.

We observed a sample of high redshift quasars ( $z\simeq 3.4, z\simeq 4.5$) in the near-infrared to measure the relative iron and Mg II emission strengths and thereby date the first star formation epoch. A detailed comparison with quasars at low-redshift show essentially the same Fe II/Mg II emission ratios and very similar continuum and line spectral properties, suggesting a lack of evolution of the relative iron to magnesium abundance of the gas since $z\simeq 4.5$ in bright quasars. These results are consistent with major star formation activity in the host galaxies beginning at an epoch corresponding to $z_f \simeq 10$, when the age of the universe was less than 0.5 Gyrs (H _o = 72 km s^-1 Mpc $^{-1}, \Omega_M = 0.3, \Omega_\Lambda = 0.7$).