In the context of the “ missing metals problem ” , the contributions of the UV-selected z \simeq 2.2 “ BX ” galaxies and z \simeq 2.5 “ distant red galaxies ” ( DRGs ) have not been discussed previously .
Here we show that : ( i ) DRGs only make a marginal contribution to the metal budget ( \sim 5 % ) ; ( ii ) BX galaxies contribute as much as 18 % to the metal budget ; and ( iii ) the K -bright subsample ( K < 20 ) of the BX sample ( roughly equivalent to the ‘ BzK ’ selected samples ) contributes roughly half of this 18 % , owing both to their larger stellar masses and higher metallicities , implying that the rare K -bright galaxies at z > 2 are a major source of metals in the budget .
We showed in the first paper of this series that submm galaxies ( SMGs ) brighter than 3 mJy contribute \sim 5 % ( \la 9 % as an upper limit ) to the metal budget .
Adding the contribution of SMGs and damped Ly \alpha absorbers , to the contribution of UV selected galaxies , implies that at least 30 % of the metals ( in galaxies ) have been accounted for at z \simeq 2 .
The cosmic metal density thus accounted for is \rho _ { Z, galaxies } \simeq 1.3 \times 10 ^ { 6 } \hbox { M$ { } _ { \odot } $ Mpc$ { } ^ { -3 % } $ } or in terms of the closure density , \Omega _ { Z } = 9.6 \times 10 ^ { -6 } .
This is a lower limit given that galaxies on the faint-end of the luminosity function are not included .
An estimate of the distribution of metals in local galaxies as a function luminosity suggests that galaxies with luminosity < L ^ { \star } contribute about half of the total mass of metals .
If the metals in galaxies at z \sim 2 are similarly distributed then faint galaxies alone can not solve the ‘ missing metals problem. ’ Galaxy populations at z \sim 2 only account for about 50 % of the total metals predicted .