This thesis clarifies the role of disk components embedded in the spheroids of early type galaxies, with particular focus on the frequency and structure of disks in galaxies conventionally classified as "ellipticals". We discuss both photometric and spectroscopic means of assessing disks. Using simple photometric models, we explore what physical disk parameters result in detectable photometric signatures. We discuss in particular the deviations of the projected isophotes from perfect ellipses in disk/spheroid systems. We show that a wide range of intrinsic disk-to-spheroid ratios (D/S) can produce very similar photometric signatures, depending on viewing angle. We find the distribution of observed isophote distortions in a sample of ellipticals with published surface photometry to be consistent with the D/S hypothesis, implying that about half of the sample members could contain disks with D/S ∼ 0.25. To confront our models with a more suitable set of data, we obtained surface photometry at 0.4μ and 1.6μ for a statistical sample of about 80 galaxies, comprised of both E's and S0's. Analyzing this data set we find that in any given luminosity bin of early type galaxies, one third of the objects contain disks whose detectability depends on a favourably high inclination. This fraction was estimated independently from isophote distortions and from radial luminosity profiles. The apparent smooth transition between disk galaxies and purely spheroidal objects can be explained exclusively by changes in the viewing angle, even assuming two discrete classes of early type galaxies (either having substantial disks or none at all). There is no need to invoke continuity along the Hubble sequence from E's to S0's. For the members of this sample we find a considerable range in D/S, 0.15 < D/S < 5. However, most of that variation is caused by changes in the relative scale lengths rather than by changes in disk surface brightness. To analyze kinematic signatures of disk components we develop an optimal algorithm to extract the line-of-sight velocity distribution (LOSVD) from the broadening of absorption line spectra. Analyzing the LOSVD's in two kinematically distinct cores of elliptical galaxies, we find that they can be modelled dynamically as small disks embedded in the large spheroid. The range in rotational support, 1.3 < ν/σ < 4, of these disks suggests that some of them have formed dissipatively and others through a merger event.

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Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references. / Also available by subscription via World Wide Web / xvii, 281 leaves, bound ill., charts 29 cm

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references.

Thesis (Ph.D) - Swinburne University of Technology, Faculty of Information & Communication Technologies, 2007. / A thesis presented in fulfillment of the requirements of Doctor of Philosophy, Faculty of Information and Communication Technologies, Swinburne University of Technology, 2007. Typescript. Bibliography p. 109-118.

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This paper presents the behaviour and design of axially loaded elliptical steel hollow sections filled with normal and high strength concrete. The experimental investigation was conducted with three nominal wall thickness (4mm, 5mm and 6.3mm) and different infill concrete cube strengths varied from 30 to 100 MPa. The effect of steel tube thickness, concrete strength, and confinement were discussed together with column strengths and load-axial shortening curves were evaluated. The study is limited to cross-section capacity and has not been validated at member level. Comparisons of the tests results together with other available results from the literature have been made with current design method used for the design of composite circular steel sections in Eurocode 4 and AISC codes. It was found that existing design guidance for concrete filled circular hollow sections may generally be safely applied to concrete filled elliptical steel tubes.

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Observations and analysis of globular cluster systems associated with three galaxy types are presented. Spectroscopy of globular cluster (GC) candidates in the Sculptor spirals NGC 253 and NGC 55 has identified 15 GCs in these galaxies. This spectroscopic sample, combined with plate scans, indicates total GC populations consistent with that expected for their luminosity and morphological type. From these data, we define new GC samples for spectroscopy. Radial velocities of 87 GCs in the Virgo elliptical NGC 4472 have been obtained, yielding data for 144 GCs when combined with previous studies. We find the blue GCs have significantly higher velocity dispersion than the red GCs, with little rotation in either population. The GCs dispersion profile declines slowly, yielding mass profiles consistent with X-ray data. We find a steeply rising M/L ratio, indicative of a massive dark halo surrounding this galaxy. From line-strengths of the GCs, we derive ages and metallicities for the GCs using simple stellar population (SSP) models. We find that the GCs are old and coeval and the bimodality seen in then- colours reflects metallicity rather than age differences. The GCs exhibit solar abundance ratios and both subpopulations show evidence for radial metallicity gradients. We have obtained high S/N spectra for 64 star clusters in the Large Magellanic Cloud. We measure their Lick indices to test the age and metallicity calibration of SSP models by comparison with literature values. We find our metallicities are consistent, although the values from our integrated spectra are slightly higher. The agreement of the ages for the old GCs is good, but is somewhat poorer for the youngest clusters. We obtain an age-metallicity relation for the clusters consistent with the galaxy's field stars. We show first results of a project to investigate the age and metallicity distributions of globular cluster systems using semi-analytic models of galaxy formation.

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