Photometric and spectroscopic analyses have shown that the Galactic bulge cluster Terzan 5 hosts several populations with different metallicities and ages that manifest as a double red horizontal branch (HB). A recent investigation of the massive bulge cluster NGC 6569 revealed a similar, though less extended, HB luminosity split, but little is known about the cluster's detailed chemical composition. Therefore, we have used high- resolution spectra from the Magellan-M2FS and VLT-FLAMES spectrographs to investigate the chemical compositions and radial velocity distributions of red giant branch and HB stars in NGC 6569. We found the cluster to have a mean heliocentric radial velocity of -48.8 km s(-1) (sigma = 5.3 km s(-1); 148 stars) and <[Fe/H]> = -0.87 dex (19 stars), but the cluster's 0.05 dex [Fe/H] dispersion precludes a significant metallicity spread. NGC 6569 exhibits light- and heavy-element distributions that are common among old bulge/inner Galaxy globular clusters, including clear (anti) correlations between [O/Fe], [Na/Fe], and [Al/Fe]. The light-element data suggest that NGC 6569 may be composed of at least two distinct populations, and the cluster's low <[La/Eu]> = -0.11 dex indicates significant pollution with r- process material. We confirm that both HBs contain cluster members, but metallicity and lightelement variations are largely ruled out as sources for the luminosity difference. However, He mass fraction differences as small as Delta Y similar to 0.02 cannot be ruled out and may be sufficient to reproduce the double HB.

This thesis is concerned with the dynamical evolution of globular star clusters modelled as the classical gravitational N-body problem. The models in this thesis are idealised in order to allow the detailed study of particular dynamical aspects of the cluster evolution. Examples of properties which tend to be omitted are stellar evolution, primordial binaries and the effect of an external tidal gravitational field. The methods used in this thesis are gas models, N-body models and physical arguments. One of the main topics in this thesis is gravothermal oscillations in multicomponent star clusters. The evolution of one-component globular clusters, systems with equal particle masses, is quite well understood. However, the evolution of more realistic globular clusters, with a range of particle masses, is a much more complicated matter. The condition for the on-set of gravothermal oscillations in a one-component system is simply that the number of stars is greater than a certain number ( ≈7000). In a multi-component system the relationship between the number of stars at which the gravothermal oscillations first appear and the stellar mass distribution of a cluster is a complex one. In order to investigate this phenomenon two different types of multi-component systems were studied: two-component systems (the simplest approximation of a mass spectrum, Chapter 2) and ten-component systems (which were realisations of continuous power law IMFs, Chapter 3). In both cases the critical number of stars at which gravothermal oscillations first appear are found empirically for a range of stellar mass distributions. The nature of the oscillations themselves are investigated and it is shown that the oscillations can be understood by focusing on the behaviour of the heavier stars within the cluster. A parameter Nef (de nined Mtot/mmax where Mtot is the total mass and mmax is the maximum stellar mass) acts as an approximate stability boundary for multicomponent systems.The stability boundary was found to be at Nef ~- 12000. In this Chapter 4, globular star clusters which contain a sub-system of stellar-mass black holes (BH) are investigated. This is done by considering two-component models, as these are the simplest approximation of more realistic multi-mass systems, where one component represents the BH population and the other represents all the other stars. These systems are found to undergo a long phase of evolution where the centre of the system is dominated by a BH sub-system. After mass segregation has driven most of the BH into a compact sub-system, the evolution of the BH sub-system is found to be in uenced by the cluster in which it is contained. The BH sub-system evolves in such a way as to satisfy the energy demands of the whole cluster, just as the core of a one component system must satisfies the energy demands of the whole cluster. The BH sub-system is found to exist for a significant amount of time. It takes approximately 10trh;i, where trh;i is the initial half-mass relaxation time, from the formation of the compact BH sub-system up until the time when 90% of the sub-system total mass is lost (which is of order 103 times the half-mass relaxation time of the BH sub-system at its time of formation). Based on theoretical arguments the rate of mass loss from the BH sub-system (M2) is predicted to be (βζM)/(αtrh): where M is the total mass, trh is the half-mass relaxation time, and α, β, ζ are three dimensionless parameters. (see Section 4.3 for details). An interesting consequence of this is that the rate of mass loss from the BH sub-system is approximately independent of the stellar mass ratio (m2/m1) and the total mass ratio (M2/M1) (in the range m2/m1 ≥ 10 and M2/M1 ≈ 10-2, where m1, m2 are the masses of individual low-mass and high-mass particles respectively, and M1, M2 are the corresponding total mass). The theory is found to be in reasonable agreement with most of the results of a series of N-body simulations, and all of the models if the value of ζ is suitable adjusted. Predictions based on theoretical arguments are also made about the structure of BH sub-systems. Other aspects of the evolution are also considered such as the conditions for the onset of gravothermal oscillation. The final chapter (Chapter 5) of the thesis contains some concluding comments as well as a discussion on some possible future projects, for which the results in this thesis would be useful.

by Lo Yuk-ming. / Bibliography: leaves 56-59 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1985

The gelling characteristics of whey proteins is governed by factors which affect the structural properties of the protein. To understand this structure gelling relationship, the following factors were investigated; protein concentration, heating temperature and time, pH, NaCl and sugars. The effect of these factors on the molecular structure and gelatin properties of whey protein concentrate (WPC), $ beta$-lactoglobulin ($ beta$-lg), $ alpha$-lactalbumin ($ alpha$-lac) and bovine serum albumin (BSA) were studied using polyacrylamide gel electrophoresis, HPLC, mass spectrometry, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that protein concentration affected textural properties without affecting the molecular structure of the whey proteins while heating temperature, pH and NaCl affected both molecular structure and the textural characteristics. NaCl and sugars increased the stability of whey proteins to thermal denaturation but decreased gel formation. $ beta$-lg formed an opaque gel at pH 3 and a translucent gel at pH 9; the peak temperature of denaturation was 84$ sp circ$C at pH 3 and 70$ sp circ$C at pH 9. At both acid and alkaline pH, denaturation of $ beta$-lg resulted in the formation of intermolecular $ beta$-sheet structures associated with aggregation. These $ beta$-sheet aggregate structures were also observed when $ alpha$-lac was heated at pH 3 and 5 but not at pH 7 and 9. At pH 7, heating $ alpha$-lac resulted in a loss of $ alpha$-helix, $3 sb{10}$-helix and $ beta$-sheet and an increase in turns. DSC showed two reversible transitions at 39.6$ sp circ$C (A) and 64.8$ sp circ$C (B). At pH 3, transition A was partially reversible (14%) while transition B was completely reversible. At pH 9, transitions A and B were completely irreversible and a translucent gel was formed. Bovine serum albumin (BSA) showed maximum stability to thermal denaturation at pH 5. Denaturation of BSA resulted in the loss of $

The Fabry-Pérot interferometer (FPI) was investigated as a potential tool for determining stellar elemental abundances. The FPI is a tunable narrow-band filter that makes it possible to obtain hundreds of stellar spectra simultaneously without the overhead associated with other multi-object spectroscopy techniques. This thesis used simulations and previously acquired data to investigate the FPI and develop data reduction techniques. Using observations of a CaII spectral line, an algorithm was created for fitting a Voigt profile to the spectrum segments. The values for radial velocity & equivalent width were compared to the values found by the group who supplied the data and found to agree well for the radial velocity values but there was some definite scatter in the equivalent width. These differences are attributed to different placement of the continuum level in the spectra. This curve-fitting script was modified to allow the fitting of synthetic spectra to simulated data. In this way it was possible to investigate how precise the abundance determination will be using the Robert Stobie Spectrograph's FPI mode. Large simulations showed that it will be possible to determine abundances to uncertainties of ±0.1 dex. This is an excellent result and should mean that future work using the FPI will give the results desired for large-scale s-process elemental abundance determination in globular cluster stars.

The Fabry-Pérot interferometer (FPI) was investigated as a potential tool for determining stellar elemental abundances. The FPI is a tunable narrow-band filter that makes it possible to obtain hundreds of stellar spectra simultaneously without the overhead associated with other multi-object spectroscopy techniques. This thesis used simulations and previously acquired data to investigate the FPI and develop data reduction techniques. Using observations of a CaII spectral line, an algorithm was created for fitting a Voigt profile to the spectrum segments. The values for radial velocity & equivalent width were compared to the values found by the group who supplied the data and found to agree well for the radial velocity values but there was some definite scatter in the equivalent width. These differences are attributed to different placement of the continuum level in the spectra. This curve-fitting script was modified to allow the fitting of synthetic spectra to simulated data. In this way it was possible to investigate how precise the abundance determination will be using the Robert Stobie Spectrograph's FPI mode. Large simulations showed that it will be possible to determine abundances to uncertainties of ±0.1 dex. This is an excellent result and should mean that future work using the FPI will give the results desired for large-scale s-process elemental abundance determination in globular cluster stars.

A 67" x 104" area of the metal-rich globular cluster M71 was searched for variable stars using 73 CCD frames. Using mean B and V values a colour-magnitude diagram down to V ≈ 22 is constructed. Four variables were discovered, with two more stars classed as possible candidates for variability. Phase diagrams and real time light curves are presented for all variables. One variable blue straggler (or SX Phe star) has been discovered with a period of 0.d05181. Values for the mass depend on the pulsation mode assumed for this star - (0.90 ± 0.13)M. for the first overtone mode, and (1.57 ± 0.22)M. for the fundamental mode. A second variable, of similar period (0.d06053), but with a magnitude l.m75 below the main sequence turn off was also found but it may be a field star. Two candidate eclipsing binary systems were found. The most likely period of one is 0.d37244. This value, and the shape of the light curve, suggest it may be a W UMa type variable. Its position on the CMD suggests that it too may be a field star. No period was obtainable for the other candidate binary due to a lack of phase coverage. Further data is needed to confirm and strengthen these claims. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

This thesis aims to better constrain the high-mass end of the globular cluster system (GCS) mass - Halo mass relation. This relation between the total mass contained in the globular clusters in a galaxy and the mass of its dark matter halo has been found to be nearly linear. The measured mass ration between the mass of the GCS and the halo mass, defined as eta, has been found to be constant over a large range of galaxy masses, however there is comparatively less data for galaxies with dark matter halo masses >10^13 solar masses. This research analyzes the GCSs of a sample of eleven high-mass brightest cluster galaxies (BCGs) through the use of the photometry program DOLPHOT on Hubble Space Telescope (HST) images in the F814W filter. The mass of the galaxies' GCSs were calculated from their GC radial distributions, and the dark matter halo masses were determined from the known relationship between total stellar mass and halo mass for BCGs. This research utilizes a new standardization technique to calculate the size of the GCS based on the galaxy's virial radius. These GC and halo masses were then compared to determine eta at this high-mass end, which was found to be eta=(6.84+/- 1.47)\times10^-5. When adding the sample BCGs to a catalogue of 303 lower-mass galaxies a total value for eta was found to be eta=(2.99 +/- 0.06)\times10^-5, which is within the literature range for of eta, and is both slightly higher and has a reduced uncertainty compared to the value for the catalogue galaxies alone which was found to be eta=(2.87 +/- 0.11)\times10^-5. This consistency between the eta-values of high-mass and lower-mass galaxies implies that in order for these BCGs to have such massive GCSs, a large proportion of these GCs must be accreted from galaxy mergers at late redshift. / Thesis / Master of Science (MSc)

Understanding the formation and evolution of galaxies is one of the most active areas of research in astrophysics. Hierarchical merging of proto-galactic fragments to build more massive galaxies is the current preferred model. A key prediction of this theory is that haloes of nearby galaxies should contain remnants of this assembly process in the form of tidal debris. Found in all but the smallest of dwarf galaxies, globular clusters (GC) are excellent probes of galaxy haloes. Having high luminosities, they are favourable targets in the outer regions of galaxies where the associated stellar surface brightness is low. GCs are thought to be amongst the oldest stellar systems in the Universe, and are likely born in the most significant phases of galaxy formation. Their metallicities, ages, spatial distributions and kinematics can be used to constrain the assembly history of their host galaxy. In this thesis, I explore the photometric and kinematic properties of several GC systems in our cosmological backyard, the Local Group of galaxies. The work is based on a major spectroscopic campaign, follow-up to the photometric Pan- Andromeda Archaeological Survey (PAndAS), as well as additional optical and near-IR data sets. Radial velocities are obtained for 78 GCs in the halo ofM31, 63 of which had no previous spectroscopic information. The GCs have projected radii between ∼ 20 and 140 kpc, thus sampling the true outer halo of this galaxy. In addition, GCs in the dwarf galaxies NGC 147, NGC 185 and NGC 6822 are also spectroscopically observed. By conducting a detailed kinematic analysis, I find that GCs in the outer halo of M31 exhibit coherent rotation around the minor optical axis, in the same direction as their more centrally located counterparts, but with a smaller amplitude of 86 ± 17 km s−1. There is also evidence that the velocity dispersion of the outer halo GC system decreases as a function of projected radius from theM31 centre, and this relation can be well described by a power lawof index ≈ −0.5. I detect and discuss various velocity correlations amongst GCs that lie on stellar streams in the M31 halo. Simple Monte Carlo tests show that such configurations are unlikely to form by chance, implying that significant fraction of the GCs in the M31 halo have been accreted alongside their parent dwarf galaxies. I also estimate the dynamical mass of M31 within 200 kpc to be (1.2 − 1.6) ± 0.2 × 1012 M⊙. I also characterize the GC systems of three dwarf galaxies in the Local Group: the dwarf elliptical satellites of M31, NGC 147 and NGC 185, and the isolated dwarf irregular NGC 6822. Using uniform optical and near-IR photometry, I constrain the ages and metallicities of their constituent GCs. The metallicities of the GCs around NGC 147 and NGC 185 are found to be metal-poor ([Fe/H]. −1.25 dex), while their ages are more difficult to constrain. The GCs hosted by NGC 6822 are found to be old (>9 Gyr) and to have a spread of metallicities (−1.6 . [Fe/H] . −0.4). I find close similarity between the mean optical (V − I)0 colours of the GCs hosted by these three dwarf galaxies to those located in the M31 outer halo, consistent with the idea that dwarf galaxies akin to them might have contributed toward the assembly of the M31 outer halo GC population. Analysing their kinematics, I find no evidence for systemic rotation in either of these three GC systems. Finally, I use the available GC kinematic data to calculate the dynamical masses of NGC 147, NGC 185 and NGC 6822.