Fingerprints of the hierarchical building-up of the structure on the mass-metallicity relation

We study the mass–metallicity relation of galactic systems with stellar masses larger than 109 M⊙ h−1 in Λ cold dark matter scenarios by using chemical hydrodynamical simulations. We find that this relation arises naturally as a consequence of the formation of the structure in a hierarchical scenario. The hierarchical building-up of the structure determines a characteristic stellar mass at Mc≈ 1010.2 M⊙ h−1 which exhibits approximately solar metallicities from z≈ 3 to z= 0. This characteristic mass separates galactic systems into two groups with massive ones forming most of their stars and metals at high redshift. We find evolution in the zero point and slope of the mass–metallicity relation driven mainly by the low-mass systems which exhibit the larger variations in the chemical properties. Although stellar mass and circular velocity are directly related, the correlation between circular velocity and metallicity shows a larger evolution with redshift because of the combination of chemical evolution and cosmology. The dispersion found in both relations is a function of the stellar mass and reflects the different dynamical history of evolution of the systems.