The stellar metallicity distribution of disc galaxies and bulges in cosmological simulations

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©2012 RAS ©2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.By means of high-resolution cosmological hydrodynamical simulations of Milky Way (MW) like disc galaxies, we conduct an analysis of the associated stellar metallicity distribution functions (MDFs). After undertaking a kinematic decomposition of each simulation into spheroid and disc subcomponents, we compare the predicted MDFs to those observed in the solar neighbourhood and the Galactic bulge. The effects of the star formation density threshold are visible in the star formation histories, which show a modulation in their behaviour driven by the threshold. The derived MDFs show median metallicities lower by 0.2-0.3 dex than the MDF observed locally in the disc and in the Galactic bulge. Possible reasons for this apparent discrepancy include the use of low stellar yields and/or centrally concentrated star formation. The dispersions are larger than the one of the observed MDF; this could be due to simulated discs being kinematically hotter relative to the MW. The fraction of low-metallicity stars is largely overestimated, visible from the more negatively skewed MDF with respect to the observational sample. For our fiducial MW analogue, we study the metallicity distribution of the stars born in situ relative to those formed via accretion (from disrupted satellites), and demonstrate that this low-metallicity tail to the MDF is populated primarily by accreted stars. Enhanced supernova and stellar radiation energy feedback to the surrounding interstellar media of these pre-disrupted satellites is suggested as an important regulator of the MDF skewnessLM-D acknowledges support from the Lyon Institute of Origins under grant ANR-10-LABX- 66.We thank the DEISA consortium, cofunded through EU FP6 project RI-031513 and the FP7 project RI-222919, for support within the DEISA Extreme Computing Imitativ