Journal Article

Galactic outflows and evolution of the interstellar medium

Benoit Côté, Hugo Martel, Laurent Drissen and Carmelle Robert

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 1, pages 847-861
Published in print March 2012 | ISSN: 0035-8711
Published online March 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.20362.x
Galactic outflows and evolution of the interstellar medium

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We present a model to self-consistently describe the joint evolution of starburst galaxies and the galactic wind resulting from this evolution. This model will eventually be used to provide a subgrid treatment of galactic outflows in cosmological simulations of galaxy formation and the evolution of the intergalactic medium (IGM). We combine the population synthesis code starburst99 with a semi-analytical model of galactic outflows and a model for the distribution and abundances of chemical elements inside the outflows. Starting with a galaxy mass, formation redshift and adopting a particular form for the star formation rate, we describe the evolution of the stellar populations in the galaxy, the evolution of the metallicity and chemical composition of the interstellar medium (ISM), the propagation of the galactic wind and the metal-enrichment of the IGM. The model takes into account the full energetics of the supernovae and stellar winds and their impact on the propagation of the galactic wind, the depletion of the ISM by the galactic wind and its impact on the subsequent evolution of the galaxy, as well as the evolving distributions and abundances of metals in the galactic wind. In this paper, we study the properties of the model by varying the mass of the galaxy, the star formation rate and the efficiency of star formation. Our main results are the following: (1) for a given star formation efficiency f*, a more extended period of active star formation tends to produce a galactic wind that reaches a larger extent. If f* is sufficiently large, the energy deposited by the stars completely expels the ISM. Eventually, the ISM is being replenished by mass loss from supernovae and stellar winds. (2) For galaxies with masses above 1011 M, the material ejected in the IGM always falls back on to the galaxy. Hence lower mass galaxies are the ones responsible for enriching the IGM. (3) Stellar winds play a minor role in the dynamical evolution of the galactic wind, because their energy input is small compared to supernovae. However, they contribute significantly to the chemical composition of the galactic wind. We conclude that the history of the ISM enrichment plays a determinant role in the chemical composition and extent of the galactic wind, and therefore its ability to enrich the IGM.

Keywords: supernovae: general; stars: winds, outflows; ISM: abundances; galaxies: evolution; intergalactic medium; cosmology: theory

Journal Article.  11691 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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