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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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