| Name: | Rajaram Nityananda |
| Affiliation: | International Centre for Theoretical Sciences -Tata Insitute of fundamental Research |
| Conference ID : | ASI2024_582 |
| Title : | Closure quantities for full polarisation radio interferometric observations: a graph theoretical approach |
| Authors : | Vinay Kumar, Rajaram NItyananda, Joseph Samuel |
| Authors Affiliation: | ICTS-TIFR, (International Centre for Theoretical Science of the Tata Institute of Fundamental Research) |
| Mode of Presentation: | Poster |
| Abstract Category : | Facilities, Technologies and Data science |
| Abstract : | VLBI observations such as those made by the Event Horizon Telescope have led to high-resolution images of the innermost parts of accretion disks and jets around black holes. The received signals are subject to phase and amplitude changes due to propagation through the atmosphere and/or instrumental effects, which may not always be amenable to accurate calibration. Therefore, ‘closure quantities’ or ‘invariants’ in which antenna based errors are cancelled have long been used in such studies. Recently, a framework was developed to construct such quantities,which are immune to antenna based linear signal modifications, from the observed correlations, for the case of full polarization observations (A.E. Broderick and D.W. Pesce 2020 ApJ 904 126, generalised by J.Samuel et.al Phys. Rev. Lett. 2022 128, 091101)
We use ideas from graph theory to extend this framework to a general scenario where only a subset of correlations among pairs of antennas are available, as can happen in a realistic case for a global network. We enumerate a complete set of invariants and implement an algorithm for constructing them. Some statistical aspects of model based image reconstruction based on the new invariants are also presented. |
