Properties of galaxies; photometry, kinematics, and masses. Disk galaxies, spiral patterns, bars and warps, gas content, star formation rates, chemical evolution. Elliptical galaxies: shapes. Structure of the Milky Way. The nature of dark matter.
Galaxies are an important nexus in the cosmic hierarchy: they serve as lighthouses marking out the vast cosmic structures that can span many millions of parsecs, but are fascinating in themselves as laboratories for the "small scale" processes of stellar birth and evolution. We now have images of billions of galaxies, and can observe them from a time less than a billion years after the Big Bang until the present day. We can study not only the appearance or "morphology" of galaxies, but also in some cases measure properties of their stellar populations, their quota of heavy elements, their gas content, and the internal motions (or kinematics) of their stars and gas. Although galaxies exhibit amazing diversity, they also conform to certain surprisingly tight correlations. From kinematic measurements, we can infer that galaxies contain a major unseen component that influences the motions of their stars and gas: the mysterious "dark matter". Moreover, the stars and gas that we can measure within galaxies falls far short of what we would expect for the cosmic "baryon budget". The study of modern galaxy formation focuses on trying to understand the observed demographics and correlations of galaxy properties and how these evolve over cosmic time, in the context of the "hierarchical structure formation" picture provided by the Cold Dark Matter theory.
In this course, we will warm up with a brief review of stars and radiative processes and basic cosmology. We will start our study of galaxies with our home Galaxy, the Milky Way, our sister galaxy M31 (Andromeda), and our smaller companions the Local Group dwarfs. Even this relatively small population of galaxies in our own "backyard" poses a number of unsolved puzzles. We will then cover the properties of spiral, lenticular, and elliptical galaxies in the 'nearby' Universe, and discuss the larger structures that form galaxy habitats: groups and clusters. One fascinating open question is whether galaxy properties are mainly shaped by "internal" processes or by their environment. We will discuss the evidence that many or even most galaxies harbor supermassive black holes in their nuclei. We will wind up the course with a discussion of how we can find and observe extremely distant (high redshift) galaxies, and of how galaxies were different in the past.