Syllabus

Description: Imagine a galaxy, behind another galaxy. Think you won’t see it? Think again. The mass of the galaxy in front distorts spacetime, causing the light of the galaxy behind to bend around it. The background galaxy will appear distorted, magnified, and may even be imaged multiple times - the foreground galaxy is acting as a lens.

Gravitational lensing has become one of the most powerful tools to study the Universe: it is the prime method to study the properties of dark matter on scales of galaxies and galaxy clusters; it can provide the statistically most representative census of exoplanet populations; and it can measure the composition and evolution history of the Universe.

The success story of lensing as an astrophysical tool is closely tied to technological advances, such as high-resolution imaging capabilities (e.g. the Hubble Space Telescope, adaptive optics on large ground-based telescopes, radio interferometry), large telescopes and wide-field cameras, time-resolved photometry in crowded fields, as well as advanced statistical techniques. For a number of current and future large-scale astronomical surveys such as the Large Synoptic Survey Telescope, the Euclid and WFIRST satellites, lensing is (one of) the main method(s) to constrain cosmology, i.e. to determine the properties of dark energy and dark matter.

This class will cover the lensing formalism, and discuss lensing applications and techniques. It will include a brief introduction of Bayesian statistics and Monte Carlo Markov Chains (MCMC), and several opportunities to work with actual data.

Structure: The content will be a mix of lectures, homework assignments, small projects (for example, downloading an image from the Hubble Space Telescope archive to measure strong lensing features of a galaxy and inferring its mass), and paper discussions.

Prerequisites: None, though familiarity with basic astrophysical and cosmological concepts will be helpful. The data projects can be completed using the computers at the Math SINC site, or other Linux or MacOS computers. Programming experience is not assumed; any necessary programming tools will be introduced in python. The course is also suited for advanced undergraduates.

Class times: Mondays + Wednesdays 10:00 - 11:20am
                      Frey 211

Instructor: Anja von der Linden
                      anja . vonderlinden AT stonybrook . edu
                      ESS 453

Office hour: Wed. 11:30am - 12:30pm

Textbooks: There is no textbook requirement for this class. To expand upon the material covered in class, the following textbooks are recommended:

• Schneider, Kochanek, Wambsganss: Gravitational Lensing: Strong, Weak and Micro. Proceedings of the Saas Fee lectures on Gravitational Lensing. The main chapters are also available on the web: strong, weak and micro.
• Schneider, Ehlers, Falco: Gravitational Lenses. The classic lensing textbook.
• Dodelson: Gravitational Lensing. New textbook.
• Mollerach and Roulet: Gravitational Lensing and Microlensing.

For an overview of extragalactic astronomy, including detailed introductions on lensing, the following is highly recommended:

• Schneider: Introduction to Extragalactic Astronomy and Cosmology.

Grading: 60% homework
                 20% paper / homework presentations
                 20% participation in class discussions

Example: You will learn to make animations of gravitational lensing phenomena such as this:

This shows the reconstruction of the geometry of an exoplanet discovered by microlensing, such as OGLE 2016–BLG–1195Lb. Animation by Yogesh Mehta.