FIR-Submm Metallicity Diagnostics for High-z Galaxies

The chemical properties of high-z galaxies provide important information for constraining galaxy evolutionary scenarios. However, optical metallicity diagnostics are unusable for heavily dust-enshrouded galaxies (such as submillimeter galaxies; SMGs), especially at z > 3. Here we focus on the flux ratio of [N tr] 205 mu m/[C 158 mu m to assess the metallicity of high-z SMGs. Through ALMA cycle 0 observations, we have detected the [N 205 mu m emission in a strongly [C II]-emitting SMG, LESS J033229.4-275619 at z = 4.76. The velocity-integrated [N II]/[C a] flux ratio is 0.043 +/- 0.008, that is consistent to the solar metallicity case. This result implies that the chemical evolution has progressed very rapidly in this system.