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Issue A&A
Volume 448, Number 3, March IV 2006
Page(s) 907 - 919
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20053602

A&A 448, 907-919 (2006)
DOI: 10.1051/0004-6361:20053602

Spectrophotometric properties of galaxies at intermediate redshifts (z ~ 0.2-1.0)

II. The Luminosity - Metallicity relation
F. Lamareille1, T. Contini1, J. Brinchmann2, 3, J.-F. Le Borgne1, S. Charlot2, 4 and J. Richard1

1  Laboratoire d'Astrophysique de Toulouse et Tarbes (LATT - UMR 5572), Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
    e-mail: flamare@ast.obs-mip.fr
2  Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Strasse 1 Postfach 1317, 85741 Garching, Germany
3  Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
4  Institut d'Astrophysique de Paris, CNRS, 98 bis boulevard Arago, 75014 Paris, France

(Received 9 June 2005 / Accepted 29 October 2005 )

Abstract
We present the gas-phase oxygen abundance (O/H) for a sample of 131 star-forming galaxies at intermediate redshifts (0.2<z<1.0). The sample selection, the spectroscopic observations (mainly with VLT/FORS) and associated data reduction, the photometric properties, the emission-line measurements, and the spectral classification are fully described in a companion paper (Paper I). We use two methods to estimate the O/H abundance ratio: the "standard" R23 method which is based on empirical calibrations, and the CL01 method which is based on grids of photo-ionization models and on the fitting of emission lines. For most galaxies, we have been able to solve the problem of the metallicity degeneracy between the high- and low-metallicity branches of the O/H vs. R23 relationship using various secondary indicators. The luminosity - metallicity (L-Z) relation has been derived in the B- and R-bands, with metallicities derived with the two methods ( R23 and CL01). In the analysis, we first consider our sample alone and then a larger one which includes other samples of intermediate-redshift galaxies drawn from the literature. The derived L-Z relations at intermediate redshifts are very similar (same slope) to the L-Z relation obtained for the local universe. Our sample alone only shows a small, not significant, evolution of the L-Z relation with redshift up to $z\sim1.0$. We only find statistical variations consistent with the uncertainty in the derived parameters. Including other samples of intermediate-redshift galaxies, we find however that galaxies at $z\sim1$ appear to be metal-deficient by a factor of ${\sim}3$ compared with galaxies in the local universe. For a given luminosity, they contain on average about one third of the metals locked in local galaxies.


Key words: galaxies: abundances -- galaxies: evolution -- galaxies: fundamental parameters -- galaxies: starburst

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© ESO 2006


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