Speaker: John Podczerwinski, Physics PhD Graduate Student
Abstract: This thesis is focused on the HI intensity mapping technique. I begin by reviewing basic cosmological theory and common observational techniques such as galaxy surveys and CMB studies. I then provide motivation for the use of HI intensity mapping along with a description of how such measurements are performed. I describe my research work, in particular the design of an ultra-wideband antenna and the development of foreground cleaning techniques. For the antenna project, I created an ultra-wideband design that was optimized with intensity mapping systematics in mind. This involved the use of a Vivaldi feed with optimized profile and a deep dish with and an elliptical collar. I also investigated the use of absorbers, which helped mitigate systematics but resulted in significantly lower sensitivity. The final antenna design achieved satisfactory levels of spectral smoothness, impedance matching and sensitivity to the 21cm hydrogen line. In simulations, I found that my design efforts helped reduce coupling between neighboring antenna elements, though not to the level desired. For the foreground cleaning projects, I investigated the use of Karhunen-Loève transforms in both map-space and visibility space. My project was the first to incorporate a KL transform in map space. This work however, did not seem to provide a substantial improvement over other available methods. I then conclude by discussing my opinions of and ideas for the future of HI intensity mapping.