Mathematics – Logic
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........10w&link_type=abstract
Ph.D. Thesis California Univ., San Diego.
Mathematics
Logic
7
Absorption Spectra, Cosmic Gases, Emission Spectra, Galactic Radiation, Galaxies, H I Regions, Quasars, Calcium, Far Infrared Radiation, Hydrogen, Images, Luminosity, Optical Emission Spectroscopy, Spectroscopic Analysis
Scientific paper
This dissertation reports combined observations of QSO absorption and H I emission from galaxies which comprise proximate pairs of background and foreground objects. The fortuitous juxtaposition of these QSO-galaxy 'pairs' provides unique opportunities to probe the extent and content of gas in foreground galaxies through evaluation of the incidence and strength of absorption lines in the spectra of the background QSOs. When combined with direct observations of the neutral hydrogen emission from galaxies, the high quality QSO absorption spectra help to quantify the relative distributions of hydrogen and metal-enriched gas in galaxies. We present optical, spectroscopic observations of a new sample of nine close QSO-galaxy pairs. Based on the results from previous studies, these objects were selected with strict limitations on the QSO-galaxy impact parameters. For a select subset of these galaxies, we present synthesis images of the H I emission distributions. These observations are combined with deep optical images and far-infrared fluxes of the galaxies to assess and interpret morphological and environmental conditions which may influence the absorption status. These observations are combined with the existing measurements for all pairs with similar impact parameters to form a 'complete' sample. Using the database from this sample of 22 close pairs, we provide a compilation of results for the individual sources and we draw a number of global conclusions. Naive assumptions regarding a direct correspondence between the incidence and strength of Ca II absorption and the impact parameters are invalid for these data. There does not appear to be a sharp impact parameter limit beyond which Ca II absorption is never detected, nor is there a minimum separation below which absorption is always detected. Limits on the relative abundance of Ca II and H I indicate that the QSO-galaxy pair absorption systems have gas-phase abundances of calcium which are larger than in the majority of Galactic halo sightlines. We tentatively find that the absorbing galaxies may be more luminous in the optical and far-infrared than the non-absorbers. Combined with a qualitative assessment of the galaxy morphologies and environments, we find that these results are consistent with the absorbers being characteristically more active than the non-absorbed. Tidal interactions and active star-formation play important and perhaps crucial roles in the origin of the absorbing gas. We interpret these results in the context of calcium depletion, and we briefly compare the inferred properties with those seen in higher red shift QSO absorption systems.
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