| The stellar content of the Hamburg/ESO survey. V. The metallicity distribution function of the Galactic halo (2008) | |||||||||
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Abstract | |||||||||
| We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely "best and brightest stars first". Comparison of the metallicities [Fe/H] of the stars determined from moderate-resolution (i.e., R ~ 2000) follow-up spectra with results derived from abundance analyses based on high-resolution spectra (i.e., R > 20,000) shows that the [Fe/H] estimates used for the determination of the halo MDF are accurate to within 0.3 dex once highly C-rich stars are eliminated. We determined the selection function of the HES, which must be taken into account for a proper comparison between the HES MDF with MDFs of other stellar populations or those predicted by models of Galactic chemical evolution. The latter show a reasonable agreement with the overall shape of the HES MDF for [Fe/H] > -3.6, but none predict the sharp drop at [Fe/H] ~ -3.6 present in the HES MDF. All theoretical MDFs, with the exception of the MDF predicted by the stochastic chemical enrichment model of Karlsson (2006), fail to represent the very sparse tail [Fe/H] < -4.0 observed in the HES. A comparison with the MDF of Galactic globular clusters and of dSph satellites to the Galaxy shows good agreement with the halo MDF, derived from the HES, once the selection function of the latter is included.. Comment: submitted to A&A | |||||||||
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