The chemical evolution of damped Lyman alpha systems and Lyman-limit systems at low redshift

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The so-called damped Lyman  systems (DLAs), sub-DLAs and Lyman-limit systems (LLS) represent strong intervening absorption-line systems in the spectra of distant quasars. These absorbers most likely arise in the neutral gas disks of galaxies and their surrounding gaseous halos and trace most of the neutral gas mass in the Universe. Knowledge about the chemical composition of DLAs, sub-DLAs and LLS is of fundamental importance to constrain the enrichment history of galaxies through cosmic time. Because of the small cross section of DLAs, sub-DLAs and LLS in quasar spectra and the limited amount of high-resolution ultraviolet (UV) quasar spectra, very little is known about the chemical evolution of the DLAs and LLS at redshifts z  0.5. In this project, we will use optical high-resolution spectra from VLT/UVES together with UV absorption-line data from HST/COS to analyze chemical abundances in a sample of ~ 30 DLAs, sub-DLAs and LLS at z  0.5. The combination of optical and UV data will allow us to derive accurate metallicities and dust-depletion patterns for elements like H, O, Si, N, C, Fe, Ca, Na, Ti, and others. Our study aims at improving our understanding of the metal-enrichment of galaxies and their gaseous environment in the local Universe.