No description available.

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The potential for luminosity functions (LFs) of post-turnoff stars to constrain basic cluster parameters such as age, metallicity, and helium abundance is examined in this dissertation. A review of the published LFs for the globular cluster (GC) M92 suggests that the morphology of the transition from the main sequence to the red giant branch (RGB) is sensitive to these parameters. In particular, a small bump in this region may provide an important age discriminant for GCs. A significant deficiency in the number of stars over a 2 mag interval, just below the turnoff, remains unexplained. A method of interpolating isochrones and LFs accurately from evolutionary sequences, from the lower main sequence to the RGB tip, is discussed. The interpolation scheme is based on primary interpolation points which are identified by the behaviour of the derivative [special characters omitted] along an evolutionary sequence. New BV CCD observations, calibrated with Landolt and Graham standard stars, for the old open cluster NGC 2243 and for the bright stars in the GCs NGC 288 and NGC 7099 are presented. The colour magnitude diagram (CMD) of NGC 2243 contains a strong binary star component. Comparisons with the fiducial sequences of the GC 47 Tuc (Hesser et al. 1987) indicate that the two clusters have similar abundances, while comparisons with the new oxygen-enhanced isochrones (Bergbusch & VandenBerg 1992) suggest that NGC 2243 has an age of 4-5 Gyr, and a metallicity [special characters omitted]. The morphology of both the CMD and the LF through the turnoff region cannot be attributed to the merging of the binary and single star sequences, but convective overshooting works in the correct sense to account for the differences between the isochrones and the CMD. For NGC 288 and NGC 7099, excellent overall consistency among the Zero-Age Horizontal Branch, isochrone, and LF fits is obtained for cluster ages of 14-16 Gyr. The manifestation of the transition bump in NGC 288's LF provides a particularly strong constraint on the age, since this feature becomes more prominent as the metallicity increases. R-method helium abundance estimates give Y ≈ 0.23 for NGC 288 and Y ≈ 0.31 for NGC 7099. The 2nd parameter problem is discussed in light of these results. The RGB bump, present in canonical LFs, is only weakly identified in the cumulative LF (CLF) of NGC 288, and may not be present at all in NGC 7099's CLF. However, the brightest RGB stars in both clusters are found within ≈ 0.2 mag of the RGB tip predicted by the oxygen-enhanced models. / Graduate

This investigation in the 24 Kapteyn Selected Areas along the celestial equator examined 21 red dwarf stars identified in an objective-prism survey. These stars were classified as red dwarf stars using light at wavelengths between 5800 A and 6800 A. Using calcium-hydride-based luminosity classification, this study found 13 of these stars to be red giant stars, and only 6 stars were found to be red dwarfs. One star was determined to be warm star. One star was not clearly distinguishable as a dwarf or giant. Distance calculations for the red dwarf stars found that these stars lie within 40 parsecs of the sun. / Department of Physics and Astronomy

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This is a creative practice-based photographically researched project that is contextualised by a written exegesis. I am attempting to conceptualise the apparent visual experiences that occur during the dying process, death, and rebirth as believed within Tibetan Buddhism. The Bardo of life is also relevant as it pre-ordains the visual context of the experiences within the dying, death and rebirth Bardos.Through the medium of photography, my methodology and practice are reflective of two fundamental ideas. These are: Luminosity and Illusion. They are supported by my research into the phenomenon of the 'Near Death Experience' and the Jungian concept of the conscious and subconscious mind. These states of reality are explored in relation to the Tibetan Book of the Dead's concept of the Bardo. My focus is to photograph the four elements of Earth, Fire, Air and Water as mediums familiar to all human beings and relate these in context to the Tibetan Book of the Dead's description of entering the Bardo of death. Illusion and luminosity are discovered by 'seeing' these within the four elements, and are related in context to the Tibetan Buddhists' belief of an after-death reality. This transition from the dying process into the unknown Bardo of death is supported by the familiarity of these four elements in life, and the mind's notion of reality.

This is a creative practice-based photographically researched project that is contextualised by a written exegesis. I am attempting to conceptualise the apparent visual experiences that occur during the dying process, death, and rebirth as believed within Tibetan Buddhism. The Bardo of life is also relevant as it pre-ordains the visual context of the experiences within the dying, death and rebirth Bardos.Through the medium of photography, my methodology and practice are reflective of two fundamental ideas. These are: Luminosity and Illusion. They are supported by my research into the phenomenon of the 'Near Death Experience' and the Jungian concept of the conscious and subconscious mind. These states of reality are explored in relation to the Tibetan Book of the Dead's concept of the Bardo. My focus is to photograph the four elements of Earth, Fire, Air and Water as mediums familiar to all human beings and relate these in context to the Tibetan Book of the Dead's description of entering the Bardo of death. Illusion and luminosity are discovered by 'seeing' these within the four elements, and are related in context to the Tibetan Buddhists' belief of an after-death reality. This transition from the dying process into the unknown Bardo of death is supported by the familiarity of these four elements in life, and the mind's notion of reality.

We used the near-infrared [Fe II] emission line signature to detect supernova remnants (SNRs) in the nearby starburst galaxies NGC 1569, NGC 3738 and NGC 5253. The near-infrared narrow-band imaging program has led to the detection of 10 SNR candidates in NGC 1569, 7 in NGC 5253, and none in NGC 3738. A spatially extended component to the [Fe II] line emission is observed in NGC 1569 and NGC 5253. This component dominates the integrated [Fe II] luminosity in both galaxies, the compact sources accounting for 14% and 7% of the total [Fe II] luminosity of NGC 1569 and NGC 5253, respectively. Despite the starburst environment, the [Fe II] luminosity of the individual SNRs is two orders of magnitude lower than the luminosities observed for SNRs in M82. We find that the density and the structure of the interstellar medium is a more important factor than the starburst nature of a galaxy in determining the average [Fe II] luminosity of a SNR. We caution against the blind usage of supernova rate vs. [Fe II] luminosity relations, which are most often calibrated with the average luminosity of the remnants in M82. We suggest that a significant fraction of the ISM in NGC 1569 and NGC 5253 is under the influence of SNRs. This does not appear to be the case in M82, where the impact of the SNRs is limited to high density knots. Also, we find evidence for an [Fe II]-emitting lifetime as long as 105 yrs, which contrasts with the 104 yrs derived from SNRs in M82-like galaxies. We find that the [Fe II] morphology, and the integrated luminosity observed in our sample galaxies, can be reproduced from a [Fe II]-emitting SNR population, as long as the pre-shock density is kept as low as 1 cm −3. Higher pre-shock density models are strongly rejected. We find a supernova rate of 0.006 SN/yr for NGC 1569 and 0.005 SN/yr for NGC 5253. / Graduate

Luminosity-velocity diagrams for 12 spiral galaxies in the Virgo cluster are presented. Optical rotation curves obtained for the innermost portions of eight galaxies, complemented with velocity data from the literature, are coupled with luminosity growth curves to investigate the distance indication capabilities of the initial linear branch (ILB) feature and to delve into the physical basis for the T-F relation. Luminosity growth curves are obtained from Gunn r CCD images. The ILB feature is found to have a substantially larger dispersion in slope (~0.9) (and consequently, zero point) than previously thought. Plotting the magnitude and velocity of the final point in the ILB for all the galaxies in our sample yields a tight correlation (essentially an "inner T-F relation"), with the caveat that two galaxies are rejected from the fit (one is foreground, the other is a member of a binary pair). Ramifications of this relation are briefly discussed. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.