| Summary: | We have used the Canada-France-Hawaii Telescope to obtain deep and accurate
multi-colour photometry of 19 open star clusters in our Galaxy. The
quality and size of the data set are unprecedented when compared with previous
studies of open star clusters. The clusters in the survey differ in richness,
age, metal content and location in the Galaxy and therefore provide a very
diverse database for furthering the research in several areas of astrophysics.
Some of the key issues which we address include the comparisons between the
observational results and up-to-date theoretical stellar evolutionary models,
star cluster dynamics, distance and age determinations, chemical evolution
scenarios, and star formation histories. Of particular interest is the study of
the properties of white dwarf stars, such as the initial-final mass relationship
and the upper mass limit to production. The depth gained in the present survey
(limiting V magnitude ~ 25) has allowed us to establish a large catalogue
of white dwarf candidates, and our current spectroscopic investigations will
provide the much needed observational constraints to white dwarf theoretical
models.
The colour-magnitude diagrams for the rich, young clusters in the survey
possess very tightly constrained, long main-sequences and show a much richer
cluster population than previous studies. This thesis summarizes how this was
done as well as key results for the two richest clusters in the survey, NGC 6819
and NGC 2099. For NGC 6819 we find: distance = 2500 pc, age = 2.5 Gyrs,
size = 9.5', and mass = 2600 M⊙. The cluster is found to be dynamically
evolved and exhibits mass-segregation effects. A strong cooling trail of white
dwarfs is found to be in excellent agreement with a 0.70 M⊙ theoretical white
dwarf cooling model. For NGC 2099 we find: distance = 1500 pc, age = 0.5
Gyrs, size = 13.9', and mass = 2500 M⊙. The cluster exhibits some signs
of dynamical evolution, although not as severe as for NGC 6819. The white
dwarf cooling age of NGC 2099 is found to be in excellent agreement with
the turn-off age. === Science, Faculty of === Physics and Astronomy, Department of === Graduate
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