Numerical computations have been performed to study the action of
dynamical friction on globular clusters in galaxies. Over a Hubble
time, the distribution of globular clusters can be altered
significantly by the action of dynamical friction which leads to
the destruction of massive globular clusters in galaxies. We
investigated the orbital decay rates for globular clusters in
elliptical and spiral galaxies separately and compared the tv.10
decay rates to check whether dynamical friction is responsible for
the difference observed in the luminosity functions for globular
clusters in these types of ga.1J ..ax• 1es, in the sense that more
massive globular clusters are observed in ellipticals than in
spirals.
Chapter one of the thesis discusses the determination of
extra-galactic distances by using globular clusters, based on the
assumption that the luminosity function of these systems is
invariant throughout the universe. We also show the evaluation of
the Hubble constant H , from the distance determined to the Virgo
0
cluster in this way. There are no compelling reasons to expect the
luminosity function of the globular clusters to be the same in
galaxies of all types and we report recent observations of the
differences seen in the luminosity functions in elliptical and
spiral globular cluster systems. The mechanisms which might lead
to this difference are discussed and it is concluded here that
dynamical friction might be the possible mechanism for the
depletion of massive globular clusters in spiral galaxies. Chapter two reviews and discusses the theory and formulation
of dynamical friction in detail.
The third chapter is concerned with the finding of a suitable
numerical integrator to solve the equations of motion in our
N-body calculations. Various algorithms fJJere checked and tested
for efficiency, stability and accuracy, in particular, Aarsethrs
N-body code. We finally chose a second-order predictor corrector c
Hybrid method ) for our restricted N-body code.
Chapter four deals with the galaxy models, initial conditions
for the particles that trace the density distributions in our
galaxies and the globular cluster models that go into the N-body
calculations.
In chapter five, we discuss the numerical work for globular
clusters orbiting in spiral galaxies. Preliminary results show
that resonances play an important role in the.orbital evolution of
the globular cluster. The slow orbital decay rates we have
obtained indicated that dynamical friction is not enough to
account for the observed depletion of massive globular clusters in
spirals.
Chapter six deals with the numerical work on globular
clusters in ellipticals. We did not observe much decay in the
orbits for these globular clusters, compared to the decay rates of
clusters in spirals.
In chapter seven, conclusions about this work and outlines
for future work are sketched.
