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Basic Information on imblob
Task: imblob
Purpose: Fit 2-D gaussian in an image or cube
Categories: map analysis
IMBLOB is a Miriad task which fits a 2D gaussian to a user
specified region. Only intensities larger than a specified
cutoff are fit.
The model fit is :
G(x,y) = OFFSET + AMP * exp(-(x-X0)**2/(2*A**2) +
-(y-Y0)**2/(2*B**2))
where A>B, and the x,y coordinate system is rotated by
PA degrees w.r.t. the NAXIS2 axis (astronomical convention)
towards the positive NAXIS1 axis.
A and B are the SIGMA, such that
FWHM = sqrt(8*ln2) * SIGMA = 2.355 * SIGMA
Key: in
The input image dataset name.
No default.
Key: region
Region over which the gaussian is to be fitted. Full region
specifications are supported.
Key: cutoff
Cutoff below which pixels are excluded from the fit. All points
included are weighted equally. Use a large enough negative number
to include all points.
Default: 0.0
Key: ini
If need be, this parameter can be used to supply the fitting routine
with initial conditions other than the ones it derived on its own.
The order of the parameters is: FWHM1, FWHM2 (arcsec), PA (degrees),
AMP, OFFSET, XCEN, YCEN (absolute pixel coordinates: 1..naxisN).
Default uses the derived values.
Key: fix
If you want to fix the center, enter two numbers XCEN, YCEN here.
They must be in absolute pixel coordinates. Default: not used.
Note: using this keyword overrides the XCEN, YCEN used in ini=
put will be for 2D gaussians:
Channel nr, Velocity, Xcen, Ycen(ARCSEC-REL), Xcen, Ycen (PIXEL-abs),
AMP, FWHM_major, FWHM_minor, PA (degrees),