We propose a probabilistic framework for performing simultaneous estimation of source structure and fringe-fitting parameters in Very Long Baseline Interferometry (VLBI) observations. As a first step, we demonstrate this technique through the analysis of synthetic short-duration Event Horizon Telescope (EHT) observations of various geometric source models at 230 GHz, in the presence of baseline-dependent thermal noise. We perform Bayesian parameter estimation and model selection between the different source models to obtain reliable uncertainty estimates and correlations between various source and fringe-fitting related model parameters. We also compare the Bayesian posteriors with those obtained using widely-used VLBI data reduction packages such as CASA and AIPS, by fringe-fitting 200 Monte Carlo simulations of each source model with different noise realisations, to obtain distributions of the Maximum A Posteriori (MAP) estimates. We find that, in the presence of resolved asymmetric source structure and a given array geometry, the traditional practice of fringe-fitting with a point source model yields appreciable offsets in the estimated phase residuals, potentially biasing or limiting the dynamic range of the starting model used for self-calibration. Simultaneously estimating the source structure earlier in the calibration process with formal uncertainties improves the precision and accuracy of fringe-fitting and establishes the potential of the available data especially when there is little prior information. We also note the potential applications of this method to astrometry and geodesy for specific science cases and the planned improvements to the computational performance and analyses of more complex source distributions.
Pixel-Level Calibration for Space-Based High Precision Astrometry Using Young's Fringes
Institut de Planétologie et d’Astrophysique（行星与天体物理研究所）；PYXALIS；Centre de Recherche Astrophysique de Lyon（里昂天体物理研究中心）；Centre National d’Etudes Spatiales（法国国家空间研究中心）
AVICA: A fully automated CASA pipeline for large volume VLBI data calibration
Institute of Astrophysics, Foundation for Research and Technology – Hellas（希腊研究基金会天体物理研究所）；Department of Physics, University of Crete（克里特大学物理系）；Department of Astrophysics, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University（拉德堡德大学数学、天体物理和粒子物理研究所天体物理学系）
Optical frequency comb integration in radio telescopes: advancing signal generation and phase calibration
Korea Advanced Institute of Science and Technology (KAIST)（韩国科学技术院）；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究所）；University of Science and Technology (UST)（科学技术联合大学院大学）；Max-Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；Korea Research Institute of Standards and Science (KRISS)（韩国标准与科学研究院）
