Understanding Galaxy Formation and Evolution HTML version

Understanding Galaxy Formation and
Vladimir Avila-Reese1
Instituto de Astronomıa, Universidad Nacional Autonoma de Mexico, A.P. 70-264,
The old dream of integrating into one the study of micro and macrocosmos
is now a reality. Cosmology, astrophysics, and particle physics intersect in a
scenario (but still not a theory) of cosmic structure formation and evolution
called Λ Cold Dark Matter (ΛCDM) model. This scenario emerged mainly to
explain the origin of galaxies. In these lecture notes, I first present a review
of the main galaxy properties, highlighting the questions that any theory of
galaxy formation should explain. Then, the cosmological framework and the
main aspects of primordial perturbation generation and evolution are ped-
agogically detached. Next, I focus on the “dark side” of galaxy formation,
presenting a review on ΛCDM halo assembling and properties, and on the
main candidates for non–baryonic dark matter. It is shown how the nature of
elemental particles can influence on the features of galaxies and their systems.
Finally, the complex processes of baryon dissipation inside the non–linearly
evolving CDM halos, formation of disks and spheroids, and transformation
of gas into stars are briefly described, remarking on the possibility of a few
driving factors and parameters able to explain the main body of galaxy prop-
erties. A summary and a discussion of some of the issues and open problems
of the ΛCDM paradigm are given in the final part of these notes.
1 Introduction
Our vision of the cosmic world and in particular of the whole Universe has
been changing dramatically in the last century. As we will see, galaxies were
repeatedly the main protagonist in the scene of these changes. It is about
80 years since E. Hubble established the nature of galaxies as gigantic self-
bound stellar systems and used their kinematics to show that the Universe as
a whole is expanding uniformly at the present time. Galaxies, as the building
blocks of the Universe, are also tracers of its large–scale structure and of its
evolution in the last 13 Gyrs or more. By looking inside galaxies we find
that they are the arena where stars form, evolve and collapse in constant