Building Blocks in Hierarchical Clustering Scenarios and their Connection with Damped Lyα\alpha Systems

We carried out a comprehensive analysis of the chemical properties of the interstellar medium (ISM) and the stellar population (SP) of current normal galaxies and their progenitors in a hierarchical clustering scenario. We compared the results with observations of Damped Lyman-$\alpha$ systems (DLAs) under the hypothesis that, at least, part of the observed DLAs could originate in the building blocks of today normal galaxies. We used a hydrodynamical cosmological code which includes star formation and chemical enrichment. Galaxy-like objects are identified at $z=0$ and then followed back in time. Random line-of-sights (LOS) are drawn through these structures in order to mimic Damped Lyman $\alpha$ systems. We then analysed the chemical properties of the ISM and SP along the LOS. We found that the progenitors of current galaxies in the field with mean $L <0.5 L^*$ and virial circular velocity of $100-250 {\rm km/sec}$ could be the associated DLA galaxies. For these systems we detected a trend for $$ to increase with redshift.(Abridged)Comment: 15 pages, 11 Postscript figures. Accepted to MNRA