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Issue A&A
Volume 426, Number 1, October IV 2004
Page(s) 37 - 51
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20040536



A&A 426, 37-51 (2004)
DOI: 10.1051/0004-6361:20040536

Continuous star formation in IZw18

S. Recchi1, 2, F. Matteucci3, A. D'Ercole4 and M. Tosi4

1  Institut für theoretische Physik und Astrophysik, Kiel University, Olshausenstrasse 40, 24118 Kiel, Germany
    e-mail: recchi@mpa-garching.mpg.de
2  Max-Planck Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching bei München, Germany
3  Dipartimento di Astronomia, Università di Trieste, Via GB Tiepolo, 11, 34131 Trieste, Italy
    e-mail: matteucci@ts.astro.it
4  INAF - Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
    e-mail: [annibale;tosi]@bo.astro.it

(Received 27 March 2004 / Accepted 25 May 2004 )

Abstract
We study the dynamical and chemical evolution of a galaxy similar to IZw18 under the assumption of a continuous star formation during bursts. We adopt a 2-D hydrocode coupled with detailed chemical yields originating from SNeII, SNeIa and from single intermediate-mass stars. Different nucleosynthetic yields and different IMF slopes are tested. In most of the explored cases, a galactic wind develops, mostly carrying out of the galaxy the metal-enriched gas produced by the burst itself. The chemical species with the largest escape probabilities are Fe and N. Consequently, we predict that the [ $\alpha$/Fe] and [ $\alpha$/N]  ratios outside the galaxy are lower than inside. In order to reproduce the chemical composition of IZw18, the best choice seems to be the adoption of the yields of Meynet & Maeder (2002) which take into account stellar rotation, although these authors do not follow the whole evolution of all the stars. Models with a flat IMF ( x=0.5) seem to be able to better reproduce the chemical properties of IZw18, but they inject in the gas a much larger amount of energy and the resulting galactic wind is very strong, at variance with observations. We also predict the evolution of the abundances in the H I medium and compare them with recent FUSE observations.


Key words: hydrodynamics -- ISM: abundances -- ISM: jets and outflows -- galaxies: evolution -- galaxies: individual: IZw18 -- galaxies: spiral



© ESO 2004


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