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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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