Polarization calibration techniques for new-generation VLBI

Abstract

The calibration and analysis of polarization observations in Very Long Baseline Interferometry (VLBI) requires the use of specific algorithms that suffer from several limitations, closely related to assumptions in the data properties that may not hold in observations taken with new-generation VLBI equipment. Nowadays, the instantaneous bandwidth achievable with VLBI backends can be as high as several GHz, covering several radio bands simultaneously. In addition, the sensitivity of VLBI observations with state-of-the-art equipment may reach dynamic ranges of tens of thousands, both in total intensity and in polarization. In this paper, we discuss the impact of the limitations of common VLBI polarimetry algorithms on narrow-field observations taken with modern VLBI arrays (from the VLBI Global Observing System, VGOS, to the Event Horizon Telescope, EHT) and present new software that overcomes these limitations. In particular, our software is able to perform a simultaneous fit of multiple calibrator sources, include non-linear terms in the model of the instrumental polarization and use a self-calibration approach for the estimate of the polarization leakage in the antenna receivers.

Accepted for publications in Astronomy and Astrophysics

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Cited by in corpus (23)

• First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization
• Stringent axion constraints with Event Horizon Telescope polarimetric measurements of M87${}^{\star }$
• Resolving the inner parsec of the blazar J1924-2914 with the Event Horizon Telescope
• The Event Horizon Telescope Image of the Quasar NRAO 530
• CASA on the fringe -- Development of VLBI processing capabilities for CASA
• Ordered magnetic fields around the 3C 84 central black hole
• Evidence for a toroidal magnetic field in the core of 3C 84
• MeqSilhouette v2: Spectrally-resolved polarimetric synthetic data generation for the Event Horizon Telescope
• Polarization Observations of AGN Jets: Past and Future
• Electromagnetic signatures of strong-field gravity from accreting black holes
• VLBI Astrometry of Radio Stars to Link Radio and Optical Celestial Reference Frames. I. HD 199178 $\&$ AR Lacertae
• Prospects of using closure traces directly for imaging in Very Long Baseline Interferometry
• A helical magnetic field in quasar NRAO150 revealed by Faraday rotation
• Towards an astronomical use of new-generation geodetic observations. I. From the correlator to full-polarization images
• Evidence of a non-equipartition energy regime in 1803+784 Core-shift and Faraday rotation measurements from simultaneous multi-frequency polarimetric VGOS observations
• Broad band flux-density monitoring of radio sources with the Onsala twin telescopes
• Rapid jet ejection from PKS 0215+015 coincident with a high-energy neutrino event
• New Views of Black Holes from Computational Imaging
• A unified model of feed rotation in radio telescopes and GNSS antennas
• VIPCALs: A fully automated calibration pipeline for very long baseline interferometry data
• A revised view of the linear polarization in the subparsec core of M87 at 7 mm