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Issue A&A
Volume 398, Number 3, February II 2003
Page(s) 891 - 899
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20021697



A&A 398, 891-899 (2003)
DOI: 10.1051/0004-6361:20021697

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

M. Dietrich1, 2, 3, I. Appenzeller3, F. Hamann1, J. Heidt3, K. Jäger4, M. Vestergaard5 and S. J. Wagner3

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  Current address: 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

(Received 17 September 2002 / Accepted 14 November 2002)

Abstract
We present observations of 11 high redshift quasars ( $3.9 \la z \la 5.0$) 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 $Z/Z_\odot = 4.3 \pm 0.3$. Assuming a chemical evolution time scale of $\tau_{{\rm evol}} \simeq 0.5 - 0.8$ Gyrs, we derive a redshift of $z_{\rm f} \simeq 6 ~{\rm to}~ 8$ for the onset of the first major star formation episode ( H0 = 65 km s -1 Mpc -1, $\Omega _{\rm M} = 0.3$, $\Omega _\Lambda = 0.7$), 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.


Key words: galaxies: active -- quasars: emission lines -- galaxies: abundances

Offprint request: M. Dietrich, dietrich@chara.gsu.edu

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© ESO 2003


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