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Basic Information on velimage
Task: velimage
Purpose: Make (x,y,z) image from an (x,y) image and model z-values.
Categories: image analysis
VELIMAGE is a MIRIAD task to make an (x,y,z) image from an (x,y)
image and a model for the z-values and dispersion. The z-values,
for example the mean velocity, are input as an (x,y) image, whilst
the dispersion can be input as either an (x,y) image or a fixed
value. The output image is formed as:-
out(x,y,z) = in1(x,y) * exp(-(z-in2(x,y))**2/(2*sigma**2)))
VELIMAGE can be used to compare models with the data. For example
one can generate a model image corresponding to a rotating galaxy,
convolve it with the actual beam and subtract the model from the
data to determine if there is residual emission which deviates from
the model rotation curve.
Key: in
The input image names, separated by commas. The first image is the
(x,y) intensity distribution integrated over the z-axis. No default.
e.g. velocity-integrated image. The second image is an (x,y) model
for the z-values, e.g. a mean velocity image. No default.
A 3rd input image gives the z-dispersion at each point. e.g. a
velocity dispersion image. If the 3rd image is not specified then
fixed dispersion, sigma must be specified.
Key: region
Region of image to be used. The default region is the entire image.
See documentation on region for details. All pixels within the
bounding box are used; pixel masking is not used.
Key: sigma
Fixed value for z-dispersion if not specified by 3rd input image.
Key: nchan
Number of channels for z-axis of output image. Default=1.
Key: start
Starting value for z-axis of output image. No default.
Key: step
Interval for z-axis of output image. No default.
Key: out
The output (x,y,z) image. No default.
Key: options
Options. Minimum match is active.
relax ignore axis descriptor mismatches
(e.g. pixel increments etc). Use with care.