Intrinsic cross-polarization ratio maps from all-sky observations with the SKA-Low prototype station Aperture Array Verification System 2

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Abstract
Precise polarimetric measurements of radio signals from the sky are crucial for achieving many scientific goals of modern and future radio telescopes. A key figure of merit (FoM) used to quantify the polarization purity of a radio polarimeter is the intrinsic cross-polarization ratio (IXR, introduced by Carozzi and Woan1). This FoM is independent of the coordinate systems and is commonly used to assess the polarimetric performance of low-frequency phased aperture arrays, such as low frequency aperture array (LOFAR),2 murchison widefield array (MWA),3 long wavelenght array (LWA),4 and the upcoming low-frequency component of the Square Kilometre Array (SKA-Low).5 Polarization calibration of such arrays is challenging due to their wide fields of view and the scarcity of polarized calibrators at these frequencies. In the literature, the various works investigating polarization performance using IXR are mostly relying on electromagnetic antenna simulations [e.g., aperture tile in focus (APERTIF),6 MWA,7 and SKA-Low8]. More recently, all-sky observations from the LOFAR-LBA Swedish station have been used to estimate the instrumental Stokes parameters across the sky and enable the computation of its IXR.9
Funding Information
  • International Centre for Radio Astronomy Research
  • MWA External Instruments Policy
  • NASA’s Astrophysics Data System

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