Strong Gravitational Lensing

The objective of this lecture is to provide a practical introduction to strong gravitational lensing including the data, the theory, and the application of strong lensing to other areas of astrophysics. This is Part 2 of the complete Saas Fee lectures on gravitational lensing. Part 1 (Schneider, this book) provides a basic introduction, Part 2 (Kochanek, this book) examines strong gravitational lenses, Part 3 (Schneider, this book) explores cluster lensing and weak lensing, and Part 4 (Wambsganss, this book) examines microlensing. It is not my objective in this lecture to provide a historical review, carefully outlining the genealogy of every development in gravitational lensing, but to focus on current research topics. Part 1 of these lectures summarizes the history of lensing and introduces most of the basic equations of lensing. The discussion is divided into 9 sections. We start in Sect. 2 with an introduction to the observational data. In Sect. 3 we outline the basic principles of strong lenses, building on the general theory of lensing from Part 1. In Sect. 4 we discuss modeling gravitational lenses and the determination of the mass distribution of lens galaxies. In Sect. 5 we discuss time delays and the Hubble constant. In Sect. 6 we discuss gravitational lens statistics and the cosmological model. In Sect. 7 we discuss the differences between galaxies and clusters as lenses. In Sect. 8 we discuss the effects of substructure or satellites on gravitational lenses. In Sect. 9 we discuss the optical properties of lens galaxies and in Sect. 10 we discuss extended sources and quasar host galaxies. Finally in Sect. 11 we discuss the future of strong gravitational lensing.