Advanced Gain Calibration Techniques in Radio Interferometry

Abstract: In this lecture, we describe a number of advanced gain calibration techniques. In particular, self-calibration is an important tool in interferometric imaging at all wavelengths. It allows the observer to determine and remove residual phase and amplitude errors that remain in the data after normal calibration while simultaneously producing a more accurate and more sensitive image of the target source. We describe the basic technique of self-calibration and attempt to dispel some common misconceptions. We proceed to give a range of useful tips, and provide continuum, spectral line, and mosaic self-calibration examples using ALMA data. We also discuss fast switching and radiometric phase correction along with advanced phase transfer techniques that can become advantageous or even essential at high frequency where the density of sufficiently bright phase calibrators becomes sparse.