EDP Sciences
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Volume 389, Number 1, July I 2002
Page(s) 106 - 114
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20020592

A&A 389, 106-114 (2002)
DOI: 10.1051/0004-6361:20020592

Chemical evolution of starburst galaxies: How does star formation proceed?

M. Mouhcine1, 2 and T. Contini1, 3

1  Observatoire Astronomique de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
2  Division of Astronomy & Astrophysics, University of California, Los Angeles, CA 90095-1562, USA
3  Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées - UMR 5572, 14 avenue E. Belin, 31400 Toulouse, France

(Received 6 August 2001 / Accepted 11 April 2002)

We compute chemical evolution models to constrain the mode and the history of star formation in starburst galaxies as a whole, i.e. over a large range of mass and metallicity. To this end, we investigate the origin of the dispersion observed in the evolution of both nitrogen-to-oxygen abundance ratio and galaxy luminosity as a function of metallicity for a large sample of starburst galaxies. We find that the variation of the star formation efficiency, in the framework of continuous star formation models, produces a scatter equivalent to that observed in the N/O versus O/H diagram for low-mass HII galaxies only. However, continous star formation models are unable to reproduce i) the scatter observed for massive starburst and UV-selected galaxies in the N/O versus O/H relation, and ii) the scatter in the MB versus O/H scaling relation observed for the whole sample of starburst galaxies. The dispersion associated with the distribution of N/O as a function of metallicity, for both low-mass and massive galaxies, is well explained in the framework of bursting star formation models. It is interpreted as a consequence of the time-delay between the ejection of nitrogen and that of oxygen into the ISM. These models also reproduce the spread observed in the luminosity-metallicity relation. Metal-rich spiral galaxies differ from metal-poor ones by a higher star formation efficiency and starburst frequency. Low-mass galaxies experienced a few bursts of star formation whereas massive spiral galaxies experienced numerous and extended powerful starbursts. Finally, we confirm previous claims (Contini et al. 2002) that UV-selected galaxies are observed at a special stage in their evolution. Their low N/O abundance ratios with respect to other starburst galaxies is well explained if they have just undergone a powerful starburst that enriched their ISM in oxygen.

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

Offprint request: T. Contini, contini@ast.obs-mip.fr

© ESO 2002