Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt........34s&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF PITTSBURGH, 1995.Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 03
Other
1
Emission Lines
Scientific paper
The geometry of the broad absorption line region of a quasi-stellar object provides an important constraint on models of QSOs. Three observational studies are presented with the primary goal of investigating the nature of the broad absorption line region (BALR) geometry on both large and small scales. Other results of general interest from these investigations are also discussed. First, a survey of brightness variations of three subsets of QSOs (radio-quiet QSOs with BALs, radio-quiet QSOs without BALs, and radio-loud QSOs) is described. The survey includes 153 objects and spans over six years of observations. It is found that the subsets of radio-quiet QSOs are marginally similar, whereas the subset of radio -loud QSOs show different variability properties. Approximately one-third of the sample show large variations, suggesting that QSOs may be further separated into finer subsets based on their variability properties. Second, a search of the available literature was made in order to consider how the incidence of broad absorption lines depends on other QSO properties. In particular, observations of QSOs in the radio, infrared, optical, ultraviolet, and x-ray regions of the spectrum are discussed. We also made HST observations of a sample of QSOs with weak doubly -ionized oxygen narrow emission lines that showed that BALs are more likely to occur in this class of object. Third, the gravitationally-lensed QSO H1413+1143 was observed in order to set constraints on the small-scale BALR geometry and possibly the sizes and shapes of the individual clouds. We show that the BALR has a flattened geometry, with a lateral extent which is much larger than the thickness along the line of sight. If radio and narrow-line emission is isotropic, the studies suggest that BALRs have a range of global covering factors, from nearly zero (radio-loud QSOs) to greater than 0.3 (QSOs with weak doubly-ionized narrow oxygen emission lines). From the observations presented here, it is difficult to conclude with any certainty that the large-scale BALR geometry must be non-spherical, although almost all recent models assume this and adopt a disk-like geometry. On the other hand, if the various observed properties of QSOs are dominated by aspect angle effects, the large-scale geometry of the BALR must be non-spherical (e.g. disk -like). However, in this case the range in global covering factor values is unclear due to uncertain model dependencies.
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