Supervisors info:
Πάνος Πάτσης Διευθυντής Ερευνών ΚΕΑΕΜ (Επιβλέπων) , Δέσποινα Χατζηδημητρίου Αναπληρώτρια Καθηγήτρια ΕΚΠΑ, Στέλιος Καζαντζίδης Επίκουρος Καθηγητής ΕΚΠΑ
Summary:
The present document consists the thesis of the MSc student Maria-Irene
Chrysafeli on the
topic of Astrophysics, Astronomy and Mechanics. The MSc program is offered by
the National
and Kapodistrian University of Athens, in the School of Science, at the Faculty
of Physics.
Subject of the dissertation is the study of the morphology of spiral galactic
models via
numerical methods. The study of the amplitude of the spiral perturbation of
galactic disks and
the understanding of the dynamics of spiral galaxies is of crucial importance
both for galactic
as well as for extragalactic astronomy. Spirals are density waves rotating in
the disks, having
their density maxima along spiral arms. The asymmetry and relative amplitude of
higher
Fourier componements of azimuthal arm profiles for the galaxies is used to
locate the main
resonances. The amplitude of the density wave and the extend of the spirals are
determined
by the linearity or non-linearity of the wave. Τhe strength of the spiral
perurbation determines
the region of the galactic disks, where linear theories can be applied to
explain the observed
structures or where the non-linear effects become important. Especially, the
amplitude of the
spiral perturbation is an indicator of nonlinear effects. The life time of a
spiral pattern to
sustain it depend on the amplitude of the perturbation itself. The general
dynamics of disks
of spiral galaxies are considerably different for weak and strong perturbations.
We study the variances of the amplitudes of spiral galaxies using the 1-D
Fourier technique.
Especially, photometric observations yield a surface brightness map, which,
assuming a constant
mass-to-light ratio, represents a surface mass density in which form all the
morphological
features are imprinted. In this study, we analyze the surface mass density in
terms of the
Fourier decomposition using a Fortran 77 algorithm and we compute the strenght
and the
phases of the Fourier componements. This technique can be applied in N-body
simulations,
galactic images in near-infrared and in response models. In our study, we
explicate the surface
mass density using the Fourier analysis for three different snapshots of
models: one response
models for the gas, for a normal spiral and other one response model for the
gas for a bar
spiral. The potentials obtained from near-infrared observations have been
studied with the
method of SPH. Also we study the snapshot of an N-body simulation of the
cumulative effect
of six dark matter substructures crossing the galactic disk and producing
several distinctive
morphological impacts in the stellar disk.
Keywords:
Morphology, Perturbations, Spirals galaxies, Structure, Numerical methods
