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Basic Information on velfit
Task: velfit
Purpose: Fit a theoretical velocity pattern to isovelocity image.
Categories: image analysis
VELFIT fits a theoretical velocity pattern to a MIRIAD
isovelocity image, weighted by the intensity image and a
geometric factor specified by model input paramaters.
The default option is to fit a rotation curve to an isovelocity
image of a rotating disk. The rotation curve and rms for the
fit are printed out and can be used to find the best fit to the
other parameters. For more details see paper by Warner, Wright
and Baldwin, 1973, MNRAS, 163,163.
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.
Key: region
Region of image to be used in the fit. See documentation on region
for details. Only the bounding box is supported.
The default region is the entire image.
Key: center
The center of the annuli in arcsec from the center pixel, measured
in the directions of RA and DEC.
Default: mapcenter as defined by crpix.
Key: pa
Position angle of ellipse major axis in degrees.
Default is 0 (north).
Key: incline
Inclination angle in degrees.
Default=0. (face on)
Key: radius
Inner and outer radii and step size along major axis in arcsecs.
The default is the whole image in steps equal to the pixel size.
Key: vsys
Center value z-axis. E.g. systemic velocity for rotation curve.
Default: 0
Key: frang
Free angle around the minor axis of points to ignore. The total angle will
be 2*frang. (1/cos(theta) problem)
Default: 0
Key: log
The output log file. The default is the terminal.
Key: options
None yet. Reserved for alternative models.