viii, 122 leaves : ill., appendices / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1970

Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1970.

Dissertation--Universität Hamburg, 1999. / Bibliogr. p. 109-113.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [117]-122).

A Hubble diagram (HD) has recently been constructed in the redshift range $0\lesssim z\lesssim 6.5$ using a non-linear relation between the ultraviolet and X-ray luminosities of QSOs. The Type Ia SN HD has already provided a high-precision test of cosmological models, but the fact that the QSO distribution extends well beyond the supernova range ($z\lesssim 1.8$), in principle provides us with an important complementary diagnostic whose significantly greater leverage in $z$ can impose tighter constraints on the distance versus redshift relationship. In this paper, we therefore perform an independent test of nine different cosmological models, among which six are expanding, while three are static. Many of these are disfavoured by other kinds of observations (including the aforementioned Type Ia SNe). We wish to examine whether the QSO HD confirms or rejects these earlier conclusions. We find that four of these models (Einstein-de Sitter, the Milne universe, the Static Universe with simple tired light and the Static universe with plasma tired light) are excluded at the $>99\%$ C.L. The Quasi-Steady State Model is excluded at $>95$\% C.L. The remaining four models ($\Lambda$CDM/$w$CDM, the $R_{\rm h}=ct$ Universe, the Friedmann open universe and a Static universe with a linear Hubble law) all pass the test. However, only $\Lambda$CDM/$w$CDM and $R_{\rm h}=ct$ also pass the Alcock-Paczy\'nski (AP) test. The optimized parameters in $\Lambda$CDM/$w$CDM are $\Omega _m=0.20^_$ and $w_{de}=-1.2^_$ (the dark-energy equation-of-state). Combined with the AP test, these values become $\Omega _m=0.38^_$ and $w_{de}=-0.28^_$. But whereas this optimization of parameters in $\Lambda$CDM/$w$CDM creates some tension with their concordance values, the $R_=ct$ Universe has the advantage of fitting the QSO and AP data without any free parameters.

Magíster en Ciencias, Mención Astronomía / In this thesis I present a search for MgII absorption systems in the resolved spectra of 10 high redshifts gravitationally lensed quasars. The goal of the thesis is to study the spatial structure of MgII systems. The quasars were observed at resolutions $R\sim4\,500$ and $R\sim40\,000$. The search yielded a sample of 31 MgII absorption systems at $0.4<z<1.6$ and probing transverse separations between lines of sight (LOS) in the range 0.29-23 $h^{-1}_{70}$ kpc. Adding systems from the literature increased the number of systems to 95. The range of transverse separation of the full sample is 0.3-100 $h^{-1}_{70}$ kpc. In this sample, the dispersion in the fractional equivalent width differences, $\Delta W_r$, decreases with equivalent width for strong systems while no high $\Delta W_r$ values are found for transverse distances $d<9$ $h^{-1}_{70}$ kpc. This is in agreement with a smooth distribution of gas at these scales. In addition, these systems show a trend of increasing $\Delta W_r$ with transverse separation. For weak systems, the dispersion in $\Delta W_r$ with respect to $W_r$ is greater than for strong systems. In this case anticoincidences (i.e., absorption in just one LOS) are found homogeneously in the range $0.2-30$ $h^{-1}_{70}$ kpc. For coincidences, $\Delta W_r$ increases with transverse separation but after $3-4$ $h^{-1}_{70}$ kpc the trend reverses. These results indicate that weak systems are more patchy or smaller than strong ones. To estimate transverse sizes, I have used two likelihood methods. The first one considers the absorption systems as spheres or disks with a uniform distribution of gas. This method yields $R\sim$ $10$ and $14$ $h^{-1}_{70}$ kpc for weak and strong systems, respectively. The second likelihood method uses the individual equivalent widths and assumes the equivalent width varies with impact parameter, i.e. $W_r=W_r(r)$. For $W_r(r)$, I tested a power law and a logarithmic function. The logarithmic function seems to be in better agreement with the data for both strong and weak systems. The second method yields $R\sim$ 20 and 40 $h^{-1}_{70}$ kpc for weak and strong systems, respectively. Thus, both methods yield smaller sizes for weak population. These sizes are much smaller than estimates using just the frequency of systems, $\frac{dN}{dz}$. Combining the results of models and observations suggests that size estimation of strong MgII systems is consistent with the assumed distribution of gas, while for weak systems the resulted sizes from the likelihood analysis seem to be overestimated. In conclusion, weak systems are predicted to be smaller ($3-4$ $h^{-1}_{70}$ kpc) and more patchy than strong systems.

We present the serendipitous discovery of a projected pair of quasi-stellar objects (QSOs) with an angular separation of Delta theta = 4.50 arcsec. The redshifts of the two QSOs are widely different: one, our program target, is a QSO with a spectrum consistent with being a narrow line Seyfert 1 active galactic nucleus at z = 2.05. For this target we detect Ly alpha, C IV, and C III]. The other QSO, which by chance was included on the spectroscopic slit, is a Type 1 QSO at a redshift of z = 1.68, for which we detect C IV, CIII], and Mg II. We compare this system to previously detected projected QSO pairs and find that only about a dozen previously known pairs have smaller angular separation.

Spectroscopic observations of fourteen broad absorption line (BAL) QSOs are presented and analyzed. Other observations are summarized. The following major conclusions are reached. Broad absorption lines (BALs) are probably present in 3 to 10 percent of the spectra of moderate to high redshift QSOs. The BALs exhibit a variety of velocity structures, from seemingly smooth, continuous absorption to complexes of individual absorption lines. Outflow velocities up to 40,000 km s⁻¹ are observed. The level of ionization is high. The minimum total absorption column densities are 10²⁰ to 10²² cm⁻². The emission line properties of BAL QSOs appear to be different from those of non-BAL QSOs. For example, N V emission is generally stronger in BAL QSOs and the emission near C III] λ1909 is generally broader in BAL QSOs. The distribution of multiplicities for isolated absorption troughs suggests that the large-scale spatial distribution of BAL clouds is non-random, possibly described by a disk geometry. The BAL clouds are incapable of accounting for all of the observed broad emission lines, particularly C III] λ1909 and Mg II λ2798. Therefore, if the BAL clouds give rise to observable emission, the generally adopted (optically thick, single component) model for the emission line region must be incorrect. Also, photoionization models, which utilize solar abundances and take the ionizing continuum to be a simple power law, are incapable of explaining the level of ionization in the BAL clouds. By considering the observed percentage of QSOs with BALs and resonance line scattering models, it is found that the absorption covering factor in BAL QSOs is between 3 and 20 percent. This suggests that possibly all, but not less than 15 percent, of the QSOs have BAL clouds associated with them. The amount of observable emission and polarization expected to be produced by the BAL clouds from resonance line scattering and collisional excitation is considered in detail. It seems likely that the BAL clouds contribute to the observed high ionization emission. A model worth exploring is one in which an inner, optically thick component gives rise to the low ionization emission, whereas an outer BAL cloud region gives rise to much of the high ionization emission.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references. / Microfiche. / xiv, 184 leaves, bound ill. 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 2000. / Includes bibliographical references. Also available on microfiche.