The chemical evolution of damped Lyman alpha systems and Lyman-limit systems at low redshift
Final Report Abstract
In this project, we have studied the dust depletion of Titanium (Ti) and Calcium (Ca) in gas in and around galaxies by analyzing Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. For this, we have used optical quasar spectra from the VLT and other instruments and analyzed the data as part of a PhD project in the years 2013-2017. The goal of this project was to explore the dust properties and enrichment history of the so-called damped Lyman alpha systems (DLAs), sub-DLAs, and Lyman-limit systems (LLS). These absorbers represent strong intervening absorption-line systems in the spectra of distant quasars and arise in the neutral gas disks of galaxies and their surrounding gaseous halos. Our systematic analysis of more than hundred absorption-line systems provides strong evidence that there are two distinct populations of Ti/Ca absorbers with either high or low Ti/Call ratios with a separation at [Ti/Ca ll]~1. Our study further indicates that the Ti/Call ratio (and possibly also the Mn/Call ratio), represents a measure for the iocal dust-to-gas ratio and is useful to distinguish between metal-rich and metal-poor absorbers and between DLAs and sub-DLAs. We demonstrate that the use of Ti/Call as diagnostic ratio provide a powerful tool to separate dust-rich environments in the star-forming regions of galaxies from dust-poor dense environments that may be typically related to cold accretion streams and outflowing gas in the course of the overall assembly and evolution of galaxies. We show that the use of Ti/Call is useful not only to study the overall dust properties in a larger sample of absorption systems, but may be used also to disentangle the multiple gas phases in individual DLAs and sub-DLAs.
Publications
- (2018) Multiple origins for the DLA at zabs = 0.313 toward PKS 1127–145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn. A&A (Astronomy & Astrophysics) 609 A85
Guber, C. R.; Richter, P.; Wendt, M.
(See online at https://doi.org/10.1051/0004-6361/201730984) - “Dust depletion of Ca and Ti in QSO absorption-line systems”. A&A 591, A137 (2017)
Guber C. & Richter P.
(See online at https://dx.doi.org/10.1051/0004-6361/201628466) - “Dust depletion of Ca and Ti in quasar absorption-line systems", Dissertation, Universität Potsdam, 2017. x, 178 S.
Christoph Guber
