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

所谓的阻尼莱曼系统(DLAS)、次DLAS系统和莱曼极限系统(LLS)代表了遥远类星体光谱中的强干涉吸收线系统。这些吸收极有可能出现在星系的中性气体盘及其周围的气晕中，并追踪宇宙中大部分的中性气体质量。对DLA、亚DLA和LLS的化学成分的了解对于通过宇宙时间限制星系的富集史是至关重要的。由于类星体光谱中DLA、亚DLA和LLS的截面很小，以及高分辨率紫外线(UV)类星体光谱的数量有限，人们对红移z0.5时DLA和LLS的化学演化知之甚少。在这个项目中，我们将使用来自真空激光雷达/UVES的光学高分辨率光谱和来自HST/COS的紫外吸收线数据来分析z0.5时约30个DLA、亚DLA和LLS样品中的化学丰度。光学和紫外光数据的结合将使我们能够得出H、O、Si、N、C、Fe、Ca、Na、Ti等元素的准确金属度和尘埃消耗模式。我们的研究旨在提高我们对星系及其在局部宇宙中的气态环境中金属丰度的理解。

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.