Physics – Optics
Scientific paper
Jun 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009phdt.........7g&link_type=abstract
Proquest Dissertations And Theses 2009. Section 0202, Part 0606 154 pages; [Ph.D. dissertation].United States -- South Carolina
Physics
Optics
Damped Lyman-Alpha, Galaxies, Quasar Absorbers
Scientific paper
In recent years, an extremely successful method to study galaxy formation and evolution, has been provided by observation of quasar absorbers. Quasar absorbers are systems intercepting our line-of-sight to a given quasar and thus produce a feature in the quasar spectrum, the so-called absorption lines. The Damped Lyman-a (DLA) and sub-Damped Lyman-a (sub-DLA) absorption features in quasar spectra are believed to be produced by intervening galaxies. However, the connection of quasar absorbers to galaxies is not well-understood, since attempts to image the absorbing galaxies have often failed. DLAs and sub-DLAs were originally thought to be the precursors of present day disk galaxies, but there is evidence that they may be dominated by gas-rich, proto-dwarf galaxies representing the basic building blocks of hierarchical growth of structure. While most DLAs appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs, has been discovered in recent spectroscopic studies. It is of great interest to image these metal-rich absorbers, especially with high spatial resolution, to understand the connection between the stellar and interstellar content of the underlying galaxies.
This dissertation consists of several projects designed to further our understanding of galaxies and galactic structures associated with intervening quasar absorption lines. Two projects were completed that involved the imaging of 13 DLA/sub-DLA galaxies at z < 1. High angular resolution near-infrared images were obtained, using the Hokupa'a Adaptive Optics system with the QUIRC near-infrared camera on the 8-m Gemini-North telescope, and the Laser Guide Star Adaptive Optics system on the 10-m Keck telescope. Detailed properties of the identified absorber galaxies are described. They are shown to be drawn from a variety of morphological types with a range of luminosities, sizes, and impact parameters. In the other set of projects, follow-up spectroscopy was performed to confirm the spectroscopic redshifts of the candidate absorbers. In addition, optical and near-infrared spectroscopy provide necessary information to understand the luminosities, dust extinction, and star formation rates and thus the nature of these galaxies. Spectroscopy of 5 DLA/sub-DLA galaxies was performed using the 10-m Keck telescope with LRIS spectrograph, and 8-m Gemini- North telescope with the GMOS spectrograph. Several emission lines (e.g., Ha, Hb, [N II], [O II], [O III]) were detected and analyzed, which revealed the redshift, metallicity, dust extinction, and star formation rate of the candidate galaxies.
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