PhD Thesis: Supernovae seen through gravitational telescopes
Monday 29 May 2017
to 13:00 at
Tanja Petrushevska (Stockholm University, Department of Physics)
Galaxies, and clusters of galaxies, can act as gravitational lenses and magnify the light of objects behind them. The effect enables observations of very distant supernovae, that otherwise would be too faint to be detected by existing telescopes,
and allows studies of the frequency and properties of these rare phenomena when the universe was young. Under the right circumstances, multiple images of the lensed supernovae can be observed, and due to the variable nature of the objects, the difference between the arrival times of the images can be measured. Since the images have taken different paths through space before reaching us, the time-differences are sensitive to the expansion rate of the universe. One class of supernovae, Type Ia, are of particular interest to detect. Their well known brightness can be used to determine the magnification, which can be used to understand the lensing systems.
In this thesis, galaxy clusters are used as gravitational telescopes to search for lensed supernovae at high redshift. Groundbased, near-infrared and optical search campaigns are described of the massive clusters Abell 1689 and 370, which are
among the most powerful gravitational telescopes known. The search resulted in the discovery of five photometrically classified, core-collapse supernovae at redshifts of 0.671