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PX397 Galaxies

Lecturer: Matteo Brogi
Weighting: 7.5 CATS

A galaxy is a system of stars, dust, stellar remnants and other bodies bound by gravity. For example, the Milky Way (our galaxy) is estimated to contain around 300bn stars and at least 100bn planets. Galaxies usually form groups, also bound by their gravitational interaction, and these groups themselves tend to be part of even larger superclusters. In this module, we will see that we can put together appealing and, sometimes quite simple, explanations of what we observe in these complex systems.

To illustrate how important physical principles, from different areas of physics, can be developed to yield a description of complex physical systems like galaxies. The module should explore some of the properties of galaxies, which yield insights into their formation, evolution and ongoing processes.

By the end of the module, students should:

  • be aware of the structure of our own Galaxy and how it fits into the ‘zoo’ of galaxies distributed through the Universe
  • understand the physical principles behind the observations used to study galaxies
  • be aware of some of the outstanding, and only partially understood, problems in the study of galaxies including the nature of galaxy cores and the roles of dark matter and dust.


The module describes both observational and theoretical classifications for different galaxy types and for our own Milky Way:

1. Galaxy classification; the Hubble Tuning Fork; elliptical and spiral galaxies; surface
brightness profiles.
2. The Milky Way, its structure and properties; the role of stellar populations and the
interstellar medium.
3. Galaxy populations; luminosity functions, star formation vs AGN, radio galaxies and
4. Galaxy kinematics; Tully-Fisher relation; rotation curves; dark matter; virial mass
5. The role and origin of dust and gas in galaxies; dust extinction laws; types of dusty galaxies
6. Introduction to galaxies at large scale: the Local Group and nearby clusters

Commitment: 15 lectures

Assessment: 1.5 hour examination

This module has a home page.

Recommended texts: S Philipps, The Structure and Evolution of Galaxies, Wiley, 2005