NOAO >   Observing Info >   Approved Programs >   2013A-0467

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Proposal Information for 2013A-0467


PI: Jian Ge, University of Florida, jge@astro.ufl.edu
Address: Astronomy Department, 211 Bryant Space Science Center, Gainesville, FL 32611, U.S.A

CoI: Fred Hamann, University of Florida
CoI: Shaohua Zhang, University of Florida
CoI: Peng Jiang, University of Science and Technology of China

Title: Chemical Enrichment History in z~1-2 Quasar 2175 ADust Absorbers

Abstract: The broad 2175 Adust feature is a ubiquitous and distinguishing feature of grains formed in the Milky Way. However, its origin, its dependence on environment, and its evolution across cosmic time are poorly understood. Thanks to the large number of available z~2-3 QSO spectra from Sloan Digital Sky Survey (SDSS) III, we have successfully identified a large homogeneous sample of 426 rare QSO absorbers at z ~ 1-2 with a strong 2175 Aextinction bump. This offers the unique opportunity to study outstanding, fundamental issues on the origin of the 2175 Abump and its evolution. The SDSS spectra show strong evolution of the bump strength with redshift and composite spectra show trends of 2175Astrength with key metal transitions (e.g. Fe II, Ti II and Zn II). We propose to use the Keck ESI optical spectrograph to study 16 systems representative of the strong 2175 \AA\ absorbers population in the range z ~ 1-2. Our primary goal is to study metal abundance and dust depletion and their correlation with the bump strength at different redshifts. The data will also allow examination of the neutral and molecular gas phases and the ISM physical conditions. Intra-comparisons within our dataset and comparisons to absorbers in the literature that lack the 2175Abump will help reveal the origin and nature of this key dust feature.


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