The Origin and Evolution of the Mass-Metallicity Relation using GalICS - Astrophysics > Cosmology and Nongalactic AstrophysicsReport as inadecuate

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Abstract: The GalICS Galaxies in Cosmological Simulations semi-analytical model ofhierar- chical galaxy formation is used to investigate the effects of differentgalactic properties, including star formation rate SFR and outflows, on theshape of the mass metallic- ity relation and to predict the relation forgalaxies at redshift z=2.27 and z=3.54. Our version of GalICS has the chemicalevolution implemented in great detail and is less heavily reliant onapproximations such as instantaneous recycling. We vary the model parameterscontrolling both the efficiency and redshift dependence of the SFR as well asthe efficiency of supernova feedback. We find that the factors controlling theSFR influence the relation significantly at all redshifts and require a strongredshift dependence, proportional to 1+z, in order to reproduce the observedrelation at the low mass end. Indeed, at any redshift, the predicted relationflattens out at the high mass end resulting in a poorer agreement withobservations in this regime. We also find that variation of the parametersassociated with outflows has a minimal effect on the relation at high redshiftbut does serve to alter its shape in the more recent past. We thus concludethat the relation is one between SFR and mass and that outflows are onlyimportant in shaping the relation at late times. When the relation isstratified by SFR it is apparent that the predicted galaxies with increasingstellar masses have higher SFRs, supporting the view that galaxy downsizing isthe origin of the relation. Attempting to reproduce the observed relation, wevary the parameters controlling the efficiency of star formation and itsredshift dependence and compare the predicted relations with Erb et al. 2006at z=2.27 and Maiolino et al. 2008 at z=3.54 in order to find thebest-fitting parameters. Abridged

Author: Jeremy Sakstein, Antonio Pipino, Julien Devriendt, Roberto Maiolino



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