Gravitational Lensing

Imagine a galaxy that lies behind another galaxy.  Will you see the galaxy in the back?  If you think not, think again.  The gravitational field of the galaxy in the front will bend the light from the background source, so that the background source appears to be distorted, magnified and can even have multiple images.  This phenomenon is gravitational lensing. 

Gravitational lensing is now a powerful astrophysical tool to study planetary systems, black holes, galaxies, clusters of galaxies and cosmology.  This course presents the underlying theory of gravitational lensing and the various astrophysical applications.

After successful completion of this module, the student is able to

• understand the working principle of gravitational lensing.
• apply gravitational lensing as an astrophysical tool to study current puzzles in astronomy such as how galaxies form and evolve, what is dark matter and what is dark energy.
• use gravitational lensing to detect matter and weigh galaxies.
• use gravitational lensing to probe the dark matter halo of the Milky Way.

No preconditions in addition to the requirements for the Master’s program in Physics.

This module consists of a lecture and exercise classes.

In classroom lectures the teaching and learning content is presented and explained in a didactical, structured, and comprehensive form. This includes basic knowledge as well as selected current topics from the research field of gravitational lensing. Crucial facts are conveyed by involving the students in scientific discussions to develop their intellectual power and to stimulate their analytic thinking on astrophysics problems. Regular attendance of the lectures is therefore highly recommended.

The presentation of the learning content is enhanced by problem examples and calculations that the students should work on a voluntary basis. These examples are intended to deepen the students' understanding and to help their learning of the course material. They are discussed at the exercise sessions to aid the students’ comprehension of the subject.

The examples as well as regular self-study of personal notes from the lectures and of textbooks are an important part of the learning process by the students. Such post-processing and practising of the teaching content is indispensable to achieve the intended learning results that the students develop the ability of explaining and applying the learned knowledge independently.

PowerPoint presentation, blackboard, discussions, post-lecture PDFs, videos, textbook, complementary literature, exercises in individual and group work, practise sheets

• P. Schneider, C. Kochanek & J. Wambsganss: Gravitational Lensing: Strong, Weak and Micro, Springer, (2006)
• S. Dodelson: Gravitational Lensing, Cambridge University Press, (2017)
• Suyu, Gould, Motta, Falco, Wambsganss, Schneider, Fassnacht, Keeton and Jimenez-Vincente: Astrophysical Applications of Gravitational Lensing, Cambridge University Press, (2016)

There will be an oral exam of about 25 minutes duration. Therein the achievement of the competencies given in section learning outcome is tested exemplarily at least to the given cognition level using comprehension questions and sample calculations.

For example an assignment in the exam might be:

• How do you use gravitational lensing to measure the mass distribution of galaxy clusters?
• How is gravitational lensing a cosmological probe?
• What is microlensing?

Participation in the exercise classes is strongly recommended since the exercises prepare for the problems of the exam and rehearse the specific competencies.