Elemental abundances in the broad emission line region of quasars at redshifts larger than 4^*

¹ Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055, USA e-mail: dietrich@astro.ufl.edu; hamann@astro.ufl.edu
² : Department of Physics & Astronomy, Georgia State University, One Park Place South SE, Suite 700, Atlanta, GA 30303, USA
³ Landessternwarte Heidelberg–Königstuhl, Königstuhl 12, 69117 Heidelberg, Germany e-mail: iappenze@lsw.uni-heidelberg.de;jheidt@lsw.uni-heidelberg.de;swagner@lsw.uni-heidelberg.de
⁴ Universitätssternwarte Göttingen, Geismarlandstraße 11, 37083 Göttingen, Germany e-mail: jaeger@uni-sw.gwdg.de
⁵ Department of Astronomy, The Ohio State University, 140 West 18th Av., Columbus, OH 43210-1173, USA e-mail: vester@astronomy.ohio-state.edu

Corresponding author: M. Dietrich, dietrich@chara.gsu.edu

Received: 17 September 2002
Accepted: 14 November 2002

Abstract

We present observations of 11 high redshift quasars () observed with low spectral resolution in the restframe ultraviolet using FORS 1 at the VLT UT 1. The emission-line fluxes of strong permitted and intercombination ultraviolet emission lines are measured to estimate the chemical composition of the line emitting gas. Comparisons to photoionization calculations indicate gas metallicities in the broad emission line region in the range of solar to several times solar. The average of the mean metallicity of each high-z quasar in this sample is . Assuming a chemical evolution time scale of  Gyrs, we derive a redshift of for the onset of the first major star formation episode ( km s^-1 Mpc^-1, , ), corresponding to an age of the universe of several 10⁸ yrs at this epoch. We note that this epoch is also supposed to be the era of re-ionization of the universe.