Interferometric polarimetry of the cosmic microwave background: Methodology

Interferometry has long been used in radio astronomy to enable imaging of astronomical sources with angular resolutions exceeding the diffraction limit of a single aperture. In the past decade, interferometry of the CMB has been carried out with instruments such as the CBI, DASI and VSA which exploited the inherent instrumental stability and simplicity of ell-space analysis of interferometer data. The practice of interferometric polarimetry has been particularly well-developed in the radio astronomical community and DASI and CBI were able to measure the polarization of the CMB over the multipole range 200 < ℓ < 1500. In this talk, I discuss the theory of interferometry and the mathematics of CMB interferometric polarimetry, using the recent polarization observations of the Cosmic Background Imager (CBI) as an example. Topics will also include description of the data pipeline, handling of contaminating signals and sources, and the construction of optimal maps. I will conclude with the possibility of future CMB interferometers with kilo-element arrays and mega-pixel imaging.