EDP Sciences
Free access
Volume 393, Number 3, October III 2002
Page(s) 809 - 819
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20021052

A&A 393, 809-819 (2002)
DOI: 10.1051/0004-6361:20021052

Evidence for chemical evolution in the spectra of high redshift galaxies

D. Mehlert1, S. Noll1, I. Appenzeller1, R. P. Saglia2, R. Bender2, A. Böhm3, N. Drory2, K. Fricke3, A. Gabasch2, J. Heidt1, U. Hopp2, K. Jäger3, C. Möllenhoff1, S. Seitz2, O. Stahl1 and B. Ziegler3

1  Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany
2  Universitätssternwarte München, Scheinerstraße 1, 81679 München, Germany
3  Universitäts-Sternwarte Göttingen, Geismarlandstraße 11, 37083 Göttingen, Germany

(Received 14 June 2002 / Accepted 1 July 2002 )

Using a sample of 57 VLT FORS spectra in the redshift range 1.37<z<3.40 (selected mainly from the FORS Deep Field survey) and a comparison sample with 36 IUE spectra of local ( $z \approx 0$) starburst galaxies we derive C IV and Si IV equivalent width values and estimate metallicities of starburst galaxies as a function of redshift. Assuming that a calibration of the C IV equivalent widths in terms of the metallicity based on the local sample of starburst galaxies is applicable to high- z objects, we find a significant increase of the average metallicities from about $ 0.16\,Z_{\odot}$ at the cosmic epoch corresponding to $z \approx 3.2$ to about $ 0.42\,Z_{\odot}$ at $z\approx 2.3$. A significant further increase in metallicity during later epochs cannot be detected in our data. Compared to the local starburst galaxies our high-redshift objects tend to be overluminous for a fixed metallicity. Our observational results are in good agreement with published observational data by other authors and with theoretical predictions of the cosmic chemical evolution.

Key words: galaxies: starburst -- galaxies: evolution -- galaxies: formation -- galaxies: stellar content -- galaxies: fundamental parameters

Offprint request: D. Mehlert, dmehlert@lsw.uni-heidelberg.de

© ESO 2002