Title: Through the Cosmic Looking Glass: Gravitational Lensing as a Tool to Observe the Most Distant Stars
Speaker:
Luke Weisenbach (Portsmouth)
Abstract:
Gravitational lensing is a powerful probe of astrophysics and cosmology. Through its ability to magnify distant sources, lensing allows us to study objects which might otherwise be unobservable. Recently, gravitational lensing has allowed for the detection of individual stars at high redshifts. Their discovery is due to a combination of lensing at two different scales however: macro-lensing by clusters of galaxies, and micro-lensing by compact objects. In this talk, I will give a basic introduction to some of the concepts behind gravitational lensing at both the macro- and micro- scale. Combining the two, I will discuss the behavior of the (micro-)images of high redshift stars as they cross the macro-caustic of a galaxy cluster. While the main focus of this talk is the theory behind *why* we can observe these stars, I will also briefly touch on how these events can be used to probe and constrain the mass fraction in compact objects at the image locations.
