The missing metals problem - III. How many metals are expelled from galaxies?

We revisit the metal budget at z ≃ 2, and include the contribution of the intergalactic medium. Past estimates of the metal budget indicated that, at redshift z ≃ 2.5, 90% of the expected metals were missing. In the first two papers of this series, we already showed that ∼30 % of the metals are observed in all z ∼ 2.5 galaxies detected in current surveys. This fraction could increase to � 60 % if one extrapolates the faint end of the LF, leaving>40 % of the metals missing. Here, we extend our analysis to the metals outside galaxies, i.e. in intergalactic medium (IGM), using (1) observational data and (2) analytical calculations. Our results for the two are strikingly similar: (1) Observationally, we find that, besides the small (5%) contribution of DLAs, the forest and sub-DLAs contribute subtantially to make �30–45 % of the metal budget, but neither of these appear to be sufficient to close the metal budget. The forest accounts for 15–30 % depending on the UV background, and sub-DLAs for �2 % to �17 % depending on the ionization fraction. Combining the metals in galaxies and in the IGM, it appears now that>65 % of the metals have been accounted for, and the