الفهرس 
Chapter 1: IntroductionOnly 14 pages are availabe for public view
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Abstract
The study of bars in spiral galaxies is an important area of research that
has led to significant progress in our understanding of galaxy evolution.
By identifying and characterizing bars in different types of galaxies, we
can gain insights into the physical processes that shape the structure and
dynamics of these systems. Spiral galaxies form a class of galaxy
originally described by Edwin Hubble in his 1936 work The Realm of the
Nebulae and, as such, form part of the Hubble sequence. Most spiral
galaxies consist of a flat, rotating disk containing stars, gas and dust, and
a central concentration of stars known as the bulge. These are often
surrounded by a much fainter halo of stars, many of which reside in
globular clusters.
Roughly two-thirds of all spirals are observed to have an additional
component in the form of a bar-like structure, extending from the central
bulge, at the ends of which the spiral arms begin. The proportion of
barred spirals relative to barless spirals has likely changed over the
history of the universe, with only about 10% containing bars about 8
billion years ago, to roughly a quarter 2.5 billion years ago, until present,
where over two-thirds of the galaxies in the visible universe (Hubble
volume) have bars.
Bars are important for the evolution of galaxies as they provide a way to
move material in and out in the disk and possibly help to spark star
formation in the central regions. They may even help feed the central
massive black hole that seems to be present in almost all galaxies. But
bars provide us with a great puzzle because we still don’t understand why
some galaxies have bars and others do not.