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3rd of December 2018
A polarisation study of Cen A
(by Anderson et al.)
ASKAP observations of linear polarisation in the southern lobe of Centaurus A have revealed extraordinarily detailed structure, showing that ASKAP will be a powerful instrument for widefield polarisation studies. It's been known for some time that the radio lobes of Centaurus A contribute to the Faraday rotation of background radio sources (as do the lobes of other radio galaxies). Where the Faraday-rotating plasma lies – throughout the lobes or on their surface – is still an unsettled question. Anderson's team took full advantage of ASKAP's wide field-of-view capability, using just 12 hours of data taken with the 16-antenna commissioning array. The observations were made over a 240 MHz band centred on 913 MHz and achieved an angular resolution of 26 x 33 arcseconds. The resulting maps of polarisation and Faraday rotation are among the most detailed ever made for radio lobes. The image above shows the ASKAP 913-MHz hue–intensity map of the southern lobe of Cen A. The hue represents Faraday depth (a measure of the amount of magnetised plasma along a sight-line); intensity is the magnitude of the polarisation vector; white contours are total flux density levels. (From Anderson et al., submitted.)

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