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21st of July 2020
ASKAP Update for July
The ASKAP Update for July is now available. In addition to news on Pilot Survey phase I data processing and features of the latest CASDA release, information is provided on improved continuum subtraction for spectral line data. Processing of Pilot Survey data showed that ASKAPsoft’s continuum subtraction approach was leaving significant residual flux around some sources. The initial scheme involved subtracting continuum flux from the visibility data using either CLEAN components derived from deconvolution, or model components derived from source finding, but science teams found examples where incomplete deconvolution, spatial complexities, or instrumental artefacts prevented accurate continuum subtraction using this initial approach. Experiments with other software packages showed that additional subtraction of a linear fit to the bandpass on frequency intervals matching the beamforming bandwidth could significantly reduce continuum residuals. The ASKAPsoft development team has developed a new continuum subtraction tool called remUVcont. The image above illustrates the improved continuum subtraction on the source MAXI J1348-630, showing remUVcont in red and the previous approach in blue. (Image credit: Wasim Raja)

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