The overall intent of these commands is described below. Please
refer to the corresponding HELP for more details about the
command syntax, options and control values.
- magentaUV_FIT is the primary fitting command. It allows to
adjust simple, analytic models of source brightness to the
current UV data. Up to 8 different source models can be combined
in a single fit 8.
The UV_FIT results can be displayed using command magentaSHOW UV_FIT.
The visibilities modeled by UV_FIT (or the fit residuals) can be
displayed using command magentaSHOW UV, either alone, or superimposed
to the current UV data.
magentaUV_FIT works on spectral line data. To optimally fit continuum
data, it is best to convert the spectrally resolved information into
a bandwidth synthesis continuum uv table.
- magentaUV_CONTINUUM converts a spectral line uv table into a
bandwidth synthesis continuum uv table. magentaUV_CONTINUUM
requires some knowledge of the field of view to evaluate how many
channels should be averaged together. This is done using the same
parameters (blueMAP_FIELD, or the product of blueMAP_SIZE
by blueMAP_CELL) and subroutines as for commands
magentaUV_STAT SETUP and magentaUV_MAP.
The bandwidth synthesis continuum uv table is peculiar
in the sense that it has several baselines for the same pair of antennas
at the same observing time: one baseline per independent frequency point,
in order to preserve optimally the angular resolution that goes as
. In practice, it is only useful for magentaUV_FIT, but
not suitable for self-calibration for example.
- magentaSHOW UV will display the best fit visibilities (stored
in the blueUV_MODEL data set) if (and only if)
the blueUVSHOW%FIT variable is set to MODEL, POINT or CURVE.
When blueUVSHOW%FIT variable is set to MODEL, the blueUV_MODEL
data set is assumed to exist, and not re-computed. It is displayed
as data points (not as a curve).
- magentaSHOW UV_FIT is intended to display the fit results
(the best fit parameter values and their errors) as a function of
channels (or velocity, or frequency). This is often a nice way to
show the detection of a signal when the signal to noise is limited,
but of course is useless for single channel data !
- magentaREAD MODEL can import the visibilities from an outside
model, so that these can be overlaid to the current UV data
by magentaSHOW UV with blueUVSHOW%FIT variable set to MODEL.
- Command magentaMODEL computes the visibilities (the blueUV_MODEL
dataset) for the best fit parameters found by magentaUV_FIT or
for the selected Clean components, depending whether magentaUV_FIT or
magentaCLEAN was used last.
- Similarly to command magentaMODEL, magentaUV_RESIDUAL computes
the residual visibilities (the blueUV_RESIDUAL data set).
- Commands magentaUV_CIRCLE magentaUV_DEPROJECT magentaUV_RADIAL
can be useful in conjunction to magentaUV_FIT, as they can provide
a (deprojected, optionally azimutally averaged) visibility data set
which can the be much more easily compared to simple, circularly
symmetric models.
Beware that the convention for angle are different
in these commands (that use the PA of the axis) and magentaUV_FIT that use the PA of the major axis: they thus differ by 90 degrees.
- Finally, command magentaUV_SELECT allow to select which data set
is displayed by magentaSHOW UV among the UV data, the blueUV_MODEL
or the blueUV_RESIDUAL.
Try magenta@ cyangag_demo:demo-uvfit for some examples.
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Gildas manager
2023-06-01