Nithyanandan Thyagarajan (CSIRO Astronomy and Space Science)Colloquium: Geometric Intuition and Image-plane Methods for Measuring Closure Phases in Interferometry |
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The Australia Telescope National Facility Colloquium | |||
15:00-16:00 Wed 03 Mar 2021 | |||
Marsfield Lecture Theatre |
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AbstractIn interferometric applications, closure phase refers to the phase of the product of spatial coherences obtained around a closed loop of interferometer elements. Its property of invariance to image-plane translation as well as to phase corruption due to the propagation and element-based instrumental effects, has been well-known for several decades. The property that this can be measured robustly even using raw and uncalibrated interferometric data makes it a true measurable physical property of the object being imaged, particularly of the degree of symmetry in the object's morphology. Therefore, it has been a valuable tool in challenging interferometric applications that otherwise require high-accuracy phase calibration. Interesting astronomical applications include the Event Horizon Telescope (EHT) imaging of the supermassive black hole event horizon at the center of M87 using very long baseline interferometry, an independent approach to statistical detection of redshifted 21 cm power spectrum of neutral Hydrogen during the epoch of reionization, and optical imaging of stellar surfaces.
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