Continuous star formation in IZw18
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 [α/Fe] and [α/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 (\cite{Mey02}) 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2004
- DOI:
- 10.1051/0004-6361:20040536
- arXiv:
- arXiv:astro-ph/0406484
- Bibcode:
- 2004A&A...426...37R
- Keywords:
-
- hydrodynamics;
- ISM: abundances;
- ISM: jets and outflows;
- galaxies: evolution;
- galaxies: individual: IZw18;
- galaxies: spiral;
- Astrophysics
- E-Print:
- 17 pages, 11 figures, accepted for publication in Astronomy and Astrophysics