In this family, most of the processing is done on the interferometric data
alone. Indeed, the interferometric data is deconvolved and corrected for
the primary beam contribution to obtain
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The method has the following free parameters: the transition radius and the
detailed shape of that transition. To avoid discontinuity, the transition
shape is chosen to be reasonably smooth. When the low resolution image
is provided by a single-dish, the best signal-to-noise combination
is obtained using a function )
and the high spatial frequencies from FFT(
).
The transition between low and high spatial frequency is selected
to use the best regions of the uv plane in both images.
that is Fourier transform
of the single-dish beam. However, that is only optimal if the noise
in this image is small enough and no other instrumental effect
(such as pointing errors or baseline ripples) affect the data. So,
can also be chosen arbitrarily. The spatial frequency of
transition is selected close to the smallest spatial frequency
reliably measured by the interferometer (e.g. about 18 m for NOEMA),
and/or the largest spatial frequency measured by the low
resolution image (e.g. about 20 m for data taken with the IRAM 30-m
telescope). For combining ACA and ALMA data, this would be 15 m,
and of ACA and 12-m single dish, about 9 m.
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Up: Algorithms to merge single-dish
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Gildas manager
2023-06-01