Gravitational Lensing of Quasars by Edge-On Spiral Galaxies

In this thesis, I studied the lensed quasar CX2201-3201, which is lensed by an edgeon spiral galaxy. The unusually high tilt of the spiral galaxy provides us with a rare opportunity for mass modeling. In addition, the unusual placement of the two visible images of the system offers an intriguing lensing system for study-the two images straddle the lensing galaxy's visible disk, but are off to one side of the light centroid. Based on mass models for the lens that are constrained by the visible disk of the galaxy, the quadrupole of the disk is strong enough to make CX2201 a "naked cusp" system, which should have three images-the two images we see, plus another located in the disk of the galaxy. We attempt to explain the absence of the third "naked cusp" image by using a series of increasingly exotic mass models. Unfortunately, none of these models turn out to be both satisfactory and a feasible solution. Although we are unable to answer the question of why the two images of CX2201 are located off to the side of the lensing galaxy's center, we gain a better understanding of the challenges this system poses for those attempting to model the lensing galaxy's mass. HST data has been obtained for the system, and although this data were obtained too late for proper inclusion in this thesis, they may aid future investigators in analyzing CX2201. Plans to obtain detailed rotation curves for the lensing galaxy are also underway, and it is the hope that future investigators will come to a better understanding of CX2201's unique features. Thesis Supervisor: Professor Paul L. Schechter Title: William A. M. Burden Professor of Astrophysics