Date of Award

Spring 2005

Document Type

Restricted Thesis

Terms of Use

© 2005 Lauren J. Willis. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Physics & Astronomy Department

First Advisor

Christopher R. Burns


A gravitational lens bends the light from a source, distorting the morphology. Further, if the lens is sufficiently strong, this distortion can produce multiple images of the original source. With multiple images that have a known time delay, one can calculate Hubble's constant. However, there is some difficulty in doing so because one needs to accurately describe the mass distribution of the lens system. One such source is 0957+561, a gravitationally lensed quasar with two resolvable images, one of which has an extended, polarized jet. Unlike the morphology, the intrinsic polarization of the jet is unchanged by gravitational lensing. We therefore predicted the deviation of the polarization from the observed morphology of the jet due to weak lensing. By simulating King, de Vaucouleurs, softened isothermal sphere (SIS), and Navarro, Frenk, and White (NFW) mass profiles for the lensing galaxy, we quantified the sensitivity of the observed lensing signal to these different models. We then combined this with the amount of mass that must be interior to the two images, which we calculated to be 8.3 * 10¹² M using strong lensing. We found that the King and SIS profiles were consistent with the data, while the cuspy profiles, de Vaucouleurs and NFW, were inconsistent with the data. This technique of using both strong and weak lensing can be applied to any source with multiple images and a jet with adequate polarization.