A MeerKAT Polarization Survey of Southern Calibration Sources

Abstract

We report on full-Stokes L-band observations of 98 MeerKAT calibration sources. Linear polarization is detected in 71 objects above a fractional level of 0.2\%. We identify ten sources with strong fractional linear polarization and low Faraday Rotation Measure that could be suitable for wide-band absolute polarization calibration. We detect significant circular polarization from 24\% of the sample down to a detection level of 0.07\%. Circularly polarized emission is seen only for flat spectrum sources $\alpha >-0.5$. We compare our polarized intensities and Faraday Synthesis results to data from the NVSS at 1400\,MHz and the ATCA SPASS survey at 2300\,MHz. NVSS data exists for 54 of our sources and SPASS data for 20 sources. The percent polarization and Rotation Measures from both surveys agree well with our results. The residual instrumental linear polarization for these observations is measured at 0.16\% and the residual instrumental circular polarization is measured at 0.05\%. These levels may reflect either instabilities in the relative bandpass between the two polarization channels with either time or antenna orientation, or atmospheric/ionospheric variations with pointing direction. Tracking of the hourly gain solutions on J0408-6545 after transfer of the primary gain solutions suggests a deterioration of the gain stability by a factor of several starting about two hours after sunrise. This suggests that observing during the nighttime could dramatically improve the precision of polarization calibration.

References in corpus (4)

• CASA, the Common Astronomy Software Applications for Radio Astronomy
• Magnetic field disorder and Faraday effects on the polarization of extragalactic radio sources
• A southern-sky total intensity source catalogue at 2.3 GHz from S-band Polarisation All-Sky Survey data
• Calibration errors in interferometric radio polarimetry

Cited by in corpus (3)

• A Formalism for Calibrating the Instrumental Polarization of Radio Interferometric Arrays at Meter Wavelengths using Unpolarized Sky: A Demonstration using the MWA Observations
• Relighting the fire in Hickson Compact Group (HCG) 15: magnetised fossil plasma revealed by the SKA Pathfinders & Precursors
• Accurate polarization calibration of FAST spectral data for measurements of Zeeman splittings of OH megamasers in IRAS 02524+2046